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    Using the API
    API overviewBeta headersErrors
    Messages
    Create a Message
    Count tokens in a Message
    Create a Message Batch
    Retrieve a Message Batch
    List Message Batches
    Cancel a Message Batch
    Delete a Message Batch
    Retrieve Message Batch results
    Models
    List Models
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    Batches

    Create a Message Batch
    messages.batches.create(BatchCreateParams**kwargs) -> MessageBatch
    POST/v1/messages/batches
    Retrieve a Message Batch
    messages.batches.retrieve(strmessage_batch_id) -> MessageBatch
    GET/v1/messages/batches/{message_batch_id}
    List Message Batches
    messages.batches.list(BatchListParams**kwargs) -> SyncPage[MessageBatch]
    GET/v1/messages/batches
    Cancel a Message Batch
    messages.batches.cancel(strmessage_batch_id) -> MessageBatch
    POST/v1/messages/batches/{message_batch_id}/cancel
    Delete a Message Batch
    messages.batches.delete(strmessage_batch_id) -> DeletedMessageBatch
    DELETE/v1/messages/batches/{message_batch_id}
    Retrieve Message Batch results
    messages.batches.results(strmessage_batch_id) -> MessageBatchIndividualResponse
    GET/v1/messages/batches/{message_batch_id}/results
    ModelsExpand Collapse
    class DeletedMessageBatch: …
    id: str

    ID of the Message Batch.

    type: Literal["message_batch_deleted"]

    Deleted object type.

    For Message Batches, this is always "message_batch_deleted".

    class MessageBatch: …
    id: str

    Unique object identifier.

    The format and length of IDs may change over time.

    archived_at: Optional[datetime]

    RFC 3339 datetime string representing the time at which the Message Batch was archived and its results became unavailable.

    cancel_initiated_at: Optional[datetime]

    RFC 3339 datetime string representing the time at which cancellation was initiated for the Message Batch. Specified only if cancellation was initiated.

    created_at: datetime

    RFC 3339 datetime string representing the time at which the Message Batch was created.

    ended_at: Optional[datetime]

    RFC 3339 datetime string representing the time at which processing for the Message Batch ended. Specified only once processing ends.

    Processing ends when every request in a Message Batch has either succeeded, errored, canceled, or expired.

    formatdate-time
    expires_at: datetime

    RFC 3339 datetime string representing the time at which the Message Batch will expire and end processing, which is 24 hours after creation.

    processing_status: Literal["in_progress", "canceling", "ended"]

    Processing status of the Message Batch.

    Accepts one of the following:
    "in_progress"
    "canceling"
    "ended"
    request_counts: MessageBatchRequestCounts

    Tallies requests within the Message Batch, categorized by their status.

    Requests start as processing and move to one of the other statuses only once processing of the entire batch ends. The sum of all values always matches the total number of requests in the batch.

    canceled: int

    Number of requests in the Message Batch that have been canceled.

    This is zero until processing of the entire Message Batch has ended.

    errored: int

    Number of requests in the Message Batch that encountered an error.

    This is zero until processing of the entire Message Batch has ended.

    expired: int

    Number of requests in the Message Batch that have expired.

    This is zero until processing of the entire Message Batch has ended.

    processing: int

    Number of requests in the Message Batch that are processing.

    succeeded: int

    Number of requests in the Message Batch that have completed successfully.

    This is zero until processing of the entire Message Batch has ended.

    results_url: Optional[str]

    URL to a .jsonl file containing the results of the Message Batch requests. Specified only once processing ends.

    Results in the file are not guaranteed to be in the same order as requests. Use the custom_id field to match results to requests.

    type: Literal["message_batch"]

    Object type.

    For Message Batches, this is always "message_batch".

    class MessageBatchCanceledResult: …
    type: Literal["canceled"]
    class MessageBatchErroredResult: …
    error: ErrorResponse
    error: ErrorObject
    Accepts one of the following:
    class InvalidRequestError: …
    message: str
    type: Literal["invalid_request_error"]
    class AuthenticationError: …
    message: str
    type: Literal["authentication_error"]
    class BillingError: …
    message: str
    type: Literal["billing_error"]
    class PermissionError: …
    message: str
    type: Literal["permission_error"]
    class NotFoundError: …
    message: str
    type: Literal["not_found_error"]
    class RateLimitError: …
    message: str
    type: Literal["rate_limit_error"]
    class GatewayTimeoutError: …
    message: str
    type: Literal["timeout_error"]
    class APIErrorObject: …
    message: str
    type: Literal["api_error"]
    class OverloadedError: …
    message: str
    type: Literal["overloaded_error"]
    request_id: Optional[str]
    type: Literal["error"]
    type: Literal["errored"]
    class MessageBatchExpiredResult: …
    type: Literal["expired"]
    class MessageBatchIndividualResponse: …

    This is a single line in the response .jsonl file and does not represent the response as a whole.

    custom_id: str

    Developer-provided ID created for each request in a Message Batch. Useful for matching results to requests, as results may be given out of request order.

    Must be unique for each request within the Message Batch.

    result: MessageBatchResult

    Processing result for this request.

    Contains a Message output if processing was successful, an error response if processing failed, or the reason why processing was not attempted, such as cancellation or expiration.

    Accepts one of the following:
    class MessageBatchSucceededResult: …
    message: Message
    id: str

    Unique object identifier.

    The format and length of IDs may change over time.

    container: Optional[Container]

    Information about the container used in the request (for the code execution tool)

    id: str

    Identifier for the container used in this request

    expires_at: datetime

    The time at which the container will expire.

    content: List[ContentBlock]

    Content generated by the model.

    This is an array of content blocks, each of which has a type that determines its shape.

    Example:

    [{"type": "text", "text": "Hi, I'm Claude."}]

    If the request input messages ended with an assistant turn, then the response content will continue directly from that last turn. You can use this to constrain the model's output.

    For example, if the input messages were:

    [
  {"role": "user", "content": "What's the Greek name for Sun? (A) Sol (B) Helios (C) Sun"},
  {"role": "assistant", "content": "The best answer is ("}
]

    Then the response content might be:

    [{"type": "text", "text": "B)"}]
    Accepts one of the following:
    class TextBlock: …
    citations: Optional[List[TextCitation]]

    Citations supporting the text block.

    The type of citation returned will depend on the type of document being cited. Citing a PDF results in page_location, plain text results in char_location, and content document results in content_block_location.

    Accepts one of the following:
    class CitationCharLocation: …
    cited_text: str
    document_index: int
    document_title: Optional[str]
    end_char_index: int
    file_id: Optional[str]
    start_char_index: int
    type: Literal["char_location"]
    class CitationPageLocation: …
    cited_text: str
    document_index: int
    document_title: Optional[str]
    end_page_number: int
    file_id: Optional[str]
    start_page_number: int
    type: Literal["page_location"]
    class CitationContentBlockLocation: …
    cited_text: str
    document_index: int
    document_title: Optional[str]
    end_block_index: int
    file_id: Optional[str]
    start_block_index: int
    type: Literal["content_block_location"]
    class CitationsWebSearchResultLocation: …
    cited_text: str
    encrypted_index: str
    title: Optional[str]
    type: Literal["web_search_result_location"]
    url: str
    class CitationsSearchResultLocation: …
    cited_text: str
    end_block_index: int
    search_result_index: int
    source: str
    start_block_index: int
    title: Optional[str]
    type: Literal["search_result_location"]
    text: str
    type: Literal["text"]
    class ThinkingBlock: …
    signature: str
    thinking: str
    type: Literal["thinking"]
    class RedactedThinkingBlock: …
    data: str
    type: Literal["redacted_thinking"]
    class ToolUseBlock: …
    id: str
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    input: Dict[str, object]
    name: str
    type: Literal["tool_use"]
    class ServerToolUseBlock: …
    id: str
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    input: Dict[str, object]
    name: Literal["web_search", "web_fetch", "code_execution", 4 more]
    Accepts one of the following:
    "web_search"
    "web_fetch"
    "code_execution"
    "bash_code_execution"
    "text_editor_code_execution"
    "tool_search_tool_regex"
    "tool_search_tool_bm25"
    type: Literal["server_tool_use"]
    class WebSearchToolResultBlock: …
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    content: WebSearchToolResultBlockContent
    Accepts one of the following:
    class WebSearchToolResultError: …
    error_code: WebSearchToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "max_uses_exceeded"
    "too_many_requests"
    "query_too_long"
    "request_too_large"
    type: Literal["web_search_tool_result_error"]
    List[WebSearchResultBlock]
    encrypted_content: str
    page_age: Optional[str]
    title: str
    type: Literal["web_search_result"]
    url: str
    tool_use_id: str
    type: Literal["web_search_tool_result"]
    class WebFetchToolResultBlock: …
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    content: Content
    Accepts one of the following:
    class WebFetchToolResultErrorBlock: …
    error_code: WebFetchToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "url_too_long"
    "url_not_allowed"
    "url_not_accessible"
    "unsupported_content_type"
    "too_many_requests"
    "max_uses_exceeded"
    "unavailable"
    type: Literal["web_fetch_tool_result_error"]
    class WebFetchBlock: …
    content: DocumentBlock
    citations: Optional[CitationsConfig]

    Citation configuration for the document

    enabled: bool
    source: Source
    Accepts one of the following:
    class Base64PDFSource: …
    data: str
    media_type: Literal["application/pdf"]
    type: Literal["base64"]
    class PlainTextSource: …
    data: str
    media_type: Literal["text/plain"]
    type: Literal["text"]
    title: Optional[str]

    The title of the document

    type: Literal["document"]
    retrieved_at: Optional[str]

    ISO 8601 timestamp when the content was retrieved

    type: Literal["web_fetch_result"]
    url: str

    Fetched content URL

    tool_use_id: str
    type: Literal["web_fetch_tool_result"]
    class CodeExecutionToolResultBlock: …
    content: CodeExecutionToolResultBlockContent

    Code execution result with encrypted stdout for PFC + web_search results.

    Accepts one of the following:
    class CodeExecutionToolResultError: …
    error_code: CodeExecutionToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    type: Literal["code_execution_tool_result_error"]
    class CodeExecutionResultBlock: …
    content: List[CodeExecutionOutputBlock]
    file_id: str
    type: Literal["code_execution_output"]
    return_code: int
    stderr: str
    stdout: str
    type: Literal["code_execution_result"]
    class EncryptedCodeExecutionResultBlock: …

    Code execution result with encrypted stdout for PFC + web_search results.

    content: List[CodeExecutionOutputBlock]
    file_id: str
    type: Literal["code_execution_output"]
    encrypted_stdout: str
    return_code: int
    stderr: str
    type: Literal["encrypted_code_execution_result"]
    tool_use_id: str
    type: Literal["code_execution_tool_result"]
    class BashCodeExecutionToolResultBlock: …
    content: Content
    Accepts one of the following:
    class BashCodeExecutionToolResultError: …
    error_code: BashCodeExecutionToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    "output_file_too_large"
    type: Literal["bash_code_execution_tool_result_error"]
    class BashCodeExecutionResultBlock: …
    content: List[BashCodeExecutionOutputBlock]
    file_id: str
    type: Literal["bash_code_execution_output"]
    return_code: int
    stderr: str
    stdout: str
    type: Literal["bash_code_execution_result"]
    tool_use_id: str
    type: Literal["bash_code_execution_tool_result"]
    class TextEditorCodeExecutionToolResultBlock: …
    content: Content
    Accepts one of the following:
    class TextEditorCodeExecutionToolResultError: …
    error_code: TextEditorCodeExecutionToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    "file_not_found"
    error_message: Optional[str]
    type: Literal["text_editor_code_execution_tool_result_error"]
    class TextEditorCodeExecutionViewResultBlock: …
    content: str
    file_type: Literal["text", "image", "pdf"]
    Accepts one of the following:
    "text"
    "image"
    "pdf"
    num_lines: Optional[int]
    start_line: Optional[int]
    total_lines: Optional[int]
    type: Literal["text_editor_code_execution_view_result"]
    class TextEditorCodeExecutionCreateResultBlock: …
    is_file_update: bool
    type: Literal["text_editor_code_execution_create_result"]
    class TextEditorCodeExecutionStrReplaceResultBlock: …
    lines: Optional[List[str]]
    new_lines: Optional[int]
    new_start: Optional[int]
    old_lines: Optional[int]
    old_start: Optional[int]
    type: Literal["text_editor_code_execution_str_replace_result"]
    tool_use_id: str
    type: Literal["text_editor_code_execution_tool_result"]
    class ToolSearchToolResultBlock: …
    content: Content
    Accepts one of the following:
    class ToolSearchToolResultError: …
    error_code: ToolSearchToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    error_message: Optional[str]
    type: Literal["tool_search_tool_result_error"]
    class ToolSearchToolSearchResultBlock: …
    tool_references: List[ToolReferenceBlock]
    tool_name: str
    type: Literal["tool_reference"]
    type: Literal["tool_search_tool_search_result"]
    tool_use_id: str
    type: Literal["tool_search_tool_result"]
    class ContainerUploadBlock: …

    Response model for a file uploaded to the container.

    file_id: str
    type: Literal["container_upload"]
    model: Model

    The model that will complete your prompt.

    See models for additional details and options.

    Accepts one of the following:
    Literal["claude-opus-4-6", "claude-sonnet-4-6", "claude-opus-4-5-20251101", 19 more]

    The model that will complete your prompt.

    See models for additional details and options.

    • claude-opus-4-6 - Most intelligent model for building agents and coding
    • claude-sonnet-4-6 - Frontier intelligence at scale — built for coding, agents, and enterprise workflows
    • claude-opus-4-5-20251101 - Premium model combining maximum intelligence with practical performance
    • claude-opus-4-5 - Premium model combining maximum intelligence with practical performance
    • claude-3-7-sonnet-latest - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-7-sonnet-20250219 - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-5-haiku-latest - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-5-haiku-20241022 - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-haiku-4-5 - Hybrid model, capable of near-instant responses and extended thinking
    • claude-haiku-4-5-20251001 - Hybrid model, capable of near-instant responses and extended thinking
    • claude-sonnet-4-20250514 - High-performance model with extended thinking
    • claude-sonnet-4-0 - High-performance model with extended thinking
    • claude-4-sonnet-20250514 - High-performance model with extended thinking
    • claude-sonnet-4-5 - Our best model for real-world agents and coding
    • claude-sonnet-4-5-20250929 - Our best model for real-world agents and coding
    • claude-opus-4-0 - Our most capable model
    • claude-opus-4-20250514 - Our most capable model
    • claude-4-opus-20250514 - Our most capable model
    • claude-opus-4-1-20250805 - Our most capable model
    • claude-3-opus-latest - Deprecated: Will reach end-of-life on January 5th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-opus-20240229 - Deprecated: Will reach end-of-life on January 5th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-haiku-20240307 - Our previous most fast and cost-effective
    Accepts one of the following:
    "claude-opus-4-6"

    Most intelligent model for building agents and coding

    "claude-sonnet-4-6"

    Frontier intelligence at scale — built for coding, agents, and enterprise workflows

    "claude-opus-4-5-20251101"

    Premium model combining maximum intelligence with practical performance

    "claude-opus-4-5"

    Premium model combining maximum intelligence with practical performance

    "claude-3-7-sonnet-latest"

    High-performance model with early extended thinking

    "claude-3-7-sonnet-20250219"

    High-performance model with early extended thinking

    "claude-3-5-haiku-latest"

    Fastest and most compact model for near-instant responsiveness

    "claude-3-5-haiku-20241022"

    Our fastest model

    "claude-haiku-4-5"

    Hybrid model, capable of near-instant responses and extended thinking

    "claude-haiku-4-5-20251001"

    Hybrid model, capable of near-instant responses and extended thinking

    "claude-sonnet-4-20250514"

    High-performance model with extended thinking

    "claude-sonnet-4-0"

    High-performance model with extended thinking

    "claude-4-sonnet-20250514"

    High-performance model with extended thinking

    "claude-sonnet-4-5"

    Our best model for real-world agents and coding

    "claude-sonnet-4-5-20250929"

    Our best model for real-world agents and coding

    "claude-opus-4-0"

    Our most capable model

    "claude-opus-4-20250514"

    Our most capable model

    "claude-4-opus-20250514"

    Our most capable model

    "claude-opus-4-1-20250805"

    Our most capable model

    "claude-3-opus-latest"

    Excels at writing and complex tasks

    "claude-3-opus-20240229"

    Excels at writing and complex tasks

    "claude-3-haiku-20240307"

    Our previous most fast and cost-effective

    str
    role: Literal["assistant"]

    Conversational role of the generated message.

    This will always be "assistant".

    stop_reason: Optional[StopReason]

    The reason that we stopped.

    This may be one the following values:

    • "end_turn": the model reached a natural stopping point
    • "max_tokens": we exceeded the requested max_tokens or the model's maximum
    • "stop_sequence": one of your provided custom stop_sequences was generated
    • "tool_use": the model invoked one or more tools
    • "pause_turn": we paused a long-running turn. You may provide the response back as-is in a subsequent request to let the model continue.
    • "refusal": when streaming classifiers intervene to handle potential policy violations

    In non-streaming mode this value is always non-null. In streaming mode, it is null in the message_start event and non-null otherwise.

    Accepts one of the following:
    "end_turn"
    "max_tokens"
    "stop_sequence"
    "tool_use"
    "pause_turn"
    "refusal"
    stop_sequence: Optional[str]

    Which custom stop sequence was generated, if any.

    This value will be a non-null string if one of your custom stop sequences was generated.

    type: Literal["message"]

    Object type.

    For Messages, this is always "message".

    usage: Usage

    Billing and rate-limit usage.

    Anthropic's API bills and rate-limits by token counts, as tokens represent the underlying cost to our systems.

    Under the hood, the API transforms requests into a format suitable for the model. The model's output then goes through a parsing stage before becoming an API response. As a result, the token counts in usage will not match one-to-one with the exact visible content of an API request or response.

    For example, output_tokens will be non-zero, even for an empty string response from Claude.

    Total input tokens in a request is the summation of input_tokens, cache_creation_input_tokens, and cache_read_input_tokens.

    cache_creation: Optional[CacheCreation]

    Breakdown of cached tokens by TTL

    ephemeral_1h_input_tokens: int

    The number of input tokens used to create the 1 hour cache entry.

    ephemeral_5m_input_tokens: int

    The number of input tokens used to create the 5 minute cache entry.

    cache_creation_input_tokens: Optional[int]

    The number of input tokens used to create the cache entry.

    cache_read_input_tokens: Optional[int]

    The number of input tokens read from the cache.

    inference_geo: Optional[str]

    The geographic region where inference was performed for this request.

    input_tokens: int

    The number of input tokens which were used.

    output_tokens: int

    The number of output tokens which were used.

    server_tool_use: Optional[ServerToolUsage]

    The number of server tool requests.

    web_fetch_requests: int

    The number of web fetch tool requests.

    web_search_requests: int

    The number of web search tool requests.

    service_tier: Optional[Literal["standard", "priority", "batch"]]

    If the request used the priority, standard, or batch tier.

    Accepts one of the following:
    "standard"
    "priority"
    "batch"
    type: Literal["succeeded"]
    class MessageBatchErroredResult: …
    error: ErrorResponse
    error: ErrorObject
    Accepts one of the following:
    class InvalidRequestError: …
    message: str
    type: Literal["invalid_request_error"]
    class AuthenticationError: …
    message: str
    type: Literal["authentication_error"]
    class BillingError: …
    message: str
    type: Literal["billing_error"]
    class PermissionError: …
    message: str
    type: Literal["permission_error"]
    class NotFoundError: …
    message: str
    type: Literal["not_found_error"]
    class RateLimitError: …
    message: str
    type: Literal["rate_limit_error"]
    class GatewayTimeoutError: …
    message: str
    type: Literal["timeout_error"]
    class APIErrorObject: …
    message: str
    type: Literal["api_error"]
    class OverloadedError: …
    message: str
    type: Literal["overloaded_error"]
    request_id: Optional[str]
    type: Literal["error"]
    type: Literal["errored"]
    class MessageBatchCanceledResult: …
    type: Literal["canceled"]
    class MessageBatchExpiredResult: …
    type: Literal["expired"]
    class MessageBatchRequestCounts: …
    canceled: int

    Number of requests in the Message Batch that have been canceled.

    This is zero until processing of the entire Message Batch has ended.

    errored: int

    Number of requests in the Message Batch that encountered an error.

    This is zero until processing of the entire Message Batch has ended.

    expired: int

    Number of requests in the Message Batch that have expired.

    This is zero until processing of the entire Message Batch has ended.

    processing: int

    Number of requests in the Message Batch that are processing.

    succeeded: int

    Number of requests in the Message Batch that have completed successfully.

    This is zero until processing of the entire Message Batch has ended.

    MessageBatchResult

    Processing result for this request.

    Contains a Message output if processing was successful, an error response if processing failed, or the reason why processing was not attempted, such as cancellation or expiration.

    Accepts one of the following:
    class MessageBatchSucceededResult: …
    message: Message
    id: str

    Unique object identifier.

    The format and length of IDs may change over time.

    container: Optional[Container]

    Information about the container used in the request (for the code execution tool)

    id: str

    Identifier for the container used in this request

    expires_at: datetime

    The time at which the container will expire.

    content: List[ContentBlock]

    Content generated by the model.

    This is an array of content blocks, each of which has a type that determines its shape.

    Example:

    [{"type": "text", "text": "Hi, I'm Claude."}]

    If the request input messages ended with an assistant turn, then the response content will continue directly from that last turn. You can use this to constrain the model's output.

    For example, if the input messages were:

    [
  {"role": "user", "content": "What's the Greek name for Sun? (A) Sol (B) Helios (C) Sun"},
  {"role": "assistant", "content": "The best answer is ("}
]

    Then the response content might be:

    [{"type": "text", "text": "B)"}]
    Accepts one of the following:
    class TextBlock: …
    citations: Optional[List[TextCitation]]

    Citations supporting the text block.

    The type of citation returned will depend on the type of document being cited. Citing a PDF results in page_location, plain text results in char_location, and content document results in content_block_location.

    Accepts one of the following:
    class CitationCharLocation: …
    cited_text: str
    document_index: int
    document_title: Optional[str]
    end_char_index: int
    file_id: Optional[str]
    start_char_index: int
    type: Literal["char_location"]
    class CitationPageLocation: …
    cited_text: str
    document_index: int
    document_title: Optional[str]
    end_page_number: int
    file_id: Optional[str]
    start_page_number: int
    type: Literal["page_location"]
    class CitationContentBlockLocation: …
    cited_text: str
    document_index: int
    document_title: Optional[str]
    end_block_index: int
    file_id: Optional[str]
    start_block_index: int
    type: Literal["content_block_location"]
    class CitationsWebSearchResultLocation: …
    cited_text: str
    encrypted_index: str
    title: Optional[str]
    type: Literal["web_search_result_location"]
    url: str
    class CitationsSearchResultLocation: …
    cited_text: str
    end_block_index: int
    search_result_index: int
    source: str
    start_block_index: int
    title: Optional[str]
    type: Literal["search_result_location"]
    text: str
    type: Literal["text"]
    class ThinkingBlock: …
    signature: str
    thinking: str
    type: Literal["thinking"]
    class RedactedThinkingBlock: …
    data: str
    type: Literal["redacted_thinking"]
    class ToolUseBlock: …
    id: str
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    input: Dict[str, object]
    name: str
    type: Literal["tool_use"]
    class ServerToolUseBlock: …
    id: str
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    input: Dict[str, object]
    name: Literal["web_search", "web_fetch", "code_execution", 4 more]
    Accepts one of the following:
    "web_search"
    "web_fetch"
    "code_execution"
    "bash_code_execution"
    "text_editor_code_execution"
    "tool_search_tool_regex"
    "tool_search_tool_bm25"
    type: Literal["server_tool_use"]
    class WebSearchToolResultBlock: …
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    content: WebSearchToolResultBlockContent
    Accepts one of the following:
    class WebSearchToolResultError: …
    error_code: WebSearchToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "max_uses_exceeded"
    "too_many_requests"
    "query_too_long"
    "request_too_large"
    type: Literal["web_search_tool_result_error"]
    List[WebSearchResultBlock]
    encrypted_content: str
    page_age: Optional[str]
    title: str
    type: Literal["web_search_result"]
    url: str
    tool_use_id: str
    type: Literal["web_search_tool_result"]
    class WebFetchToolResultBlock: …
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    content: Content
    Accepts one of the following:
    class WebFetchToolResultErrorBlock: …
    error_code: WebFetchToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "url_too_long"
    "url_not_allowed"
    "url_not_accessible"
    "unsupported_content_type"
    "too_many_requests"
    "max_uses_exceeded"
    "unavailable"
    type: Literal["web_fetch_tool_result_error"]
    class WebFetchBlock: …
    content: DocumentBlock
    citations: Optional[CitationsConfig]

    Citation configuration for the document

    enabled: bool
    source: Source
    Accepts one of the following:
    class Base64PDFSource: …
    data: str
    media_type: Literal["application/pdf"]
    type: Literal["base64"]
    class PlainTextSource: …
    data: str
    media_type: Literal["text/plain"]
    type: Literal["text"]
    title: Optional[str]

    The title of the document

    type: Literal["document"]
    retrieved_at: Optional[str]

    ISO 8601 timestamp when the content was retrieved

    type: Literal["web_fetch_result"]
    url: str

    Fetched content URL

    tool_use_id: str
    type: Literal["web_fetch_tool_result"]
    class CodeExecutionToolResultBlock: …
    content: CodeExecutionToolResultBlockContent

    Code execution result with encrypted stdout for PFC + web_search results.

    Accepts one of the following:
    class CodeExecutionToolResultError: …
    error_code: CodeExecutionToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    type: Literal["code_execution_tool_result_error"]
    class CodeExecutionResultBlock: …
    content: List[CodeExecutionOutputBlock]
    file_id: str
    type: Literal["code_execution_output"]
    return_code: int
    stderr: str
    stdout: str
    type: Literal["code_execution_result"]
    class EncryptedCodeExecutionResultBlock: …

    Code execution result with encrypted stdout for PFC + web_search results.

    content: List[CodeExecutionOutputBlock]
    file_id: str
    type: Literal["code_execution_output"]
    encrypted_stdout: str
    return_code: int
    stderr: str
    type: Literal["encrypted_code_execution_result"]
    tool_use_id: str
    type: Literal["code_execution_tool_result"]
    class BashCodeExecutionToolResultBlock: …
    content: Content
    Accepts one of the following:
    class BashCodeExecutionToolResultError: …
    error_code: BashCodeExecutionToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    "output_file_too_large"
    type: Literal["bash_code_execution_tool_result_error"]
    class BashCodeExecutionResultBlock: …
    content: List[BashCodeExecutionOutputBlock]
    file_id: str
    type: Literal["bash_code_execution_output"]
    return_code: int
    stderr: str
    stdout: str
    type: Literal["bash_code_execution_result"]
    tool_use_id: str
    type: Literal["bash_code_execution_tool_result"]
    class TextEditorCodeExecutionToolResultBlock: …
    content: Content
    Accepts one of the following:
    class TextEditorCodeExecutionToolResultError: …
    error_code: TextEditorCodeExecutionToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    "file_not_found"
    error_message: Optional[str]
    type: Literal["text_editor_code_execution_tool_result_error"]
    class TextEditorCodeExecutionViewResultBlock: …
    content: str
    file_type: Literal["text", "image", "pdf"]
    Accepts one of the following:
    "text"
    "image"
    "pdf"
    num_lines: Optional[int]
    start_line: Optional[int]
    total_lines: Optional[int]
    type: Literal["text_editor_code_execution_view_result"]
    class TextEditorCodeExecutionCreateResultBlock: …
    is_file_update: bool
    type: Literal["text_editor_code_execution_create_result"]
    class TextEditorCodeExecutionStrReplaceResultBlock: …
    lines: Optional[List[str]]
    new_lines: Optional[int]
    new_start: Optional[int]
    old_lines: Optional[int]
    old_start: Optional[int]
    type: Literal["text_editor_code_execution_str_replace_result"]
    tool_use_id: str
    type: Literal["text_editor_code_execution_tool_result"]
    class ToolSearchToolResultBlock: …
    content: Content
    Accepts one of the following:
    class ToolSearchToolResultError: …
    error_code: ToolSearchToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    error_message: Optional[str]
    type: Literal["tool_search_tool_result_error"]
    class ToolSearchToolSearchResultBlock: …
    tool_references: List[ToolReferenceBlock]
    tool_name: str
    type: Literal["tool_reference"]
    type: Literal["tool_search_tool_search_result"]
    tool_use_id: str
    type: Literal["tool_search_tool_result"]
    class ContainerUploadBlock: …

    Response model for a file uploaded to the container.

    file_id: str
    type: Literal["container_upload"]
    model: Model

    The model that will complete your prompt.

    See models for additional details and options.

    Accepts one of the following:
    Literal["claude-opus-4-6", "claude-sonnet-4-6", "claude-opus-4-5-20251101", 19 more]

    The model that will complete your prompt.

    See models for additional details and options.

    • claude-opus-4-6 - Most intelligent model for building agents and coding
    • claude-sonnet-4-6 - Frontier intelligence at scale — built for coding, agents, and enterprise workflows
    • claude-opus-4-5-20251101 - Premium model combining maximum intelligence with practical performance
    • claude-opus-4-5 - Premium model combining maximum intelligence with practical performance
    • claude-3-7-sonnet-latest - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-7-sonnet-20250219 - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-5-haiku-latest - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-5-haiku-20241022 - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-haiku-4-5 - Hybrid model, capable of near-instant responses and extended thinking
    • claude-haiku-4-5-20251001 - Hybrid model, capable of near-instant responses and extended thinking
    • claude-sonnet-4-20250514 - High-performance model with extended thinking
    • claude-sonnet-4-0 - High-performance model with extended thinking
    • claude-4-sonnet-20250514 - High-performance model with extended thinking
    • claude-sonnet-4-5 - Our best model for real-world agents and coding
    • claude-sonnet-4-5-20250929 - Our best model for real-world agents and coding
    • claude-opus-4-0 - Our most capable model
    • claude-opus-4-20250514 - Our most capable model
    • claude-4-opus-20250514 - Our most capable model
    • claude-opus-4-1-20250805 - Our most capable model
    • claude-3-opus-latest - Deprecated: Will reach end-of-life on January 5th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-opus-20240229 - Deprecated: Will reach end-of-life on January 5th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-haiku-20240307 - Our previous most fast and cost-effective
    Accepts one of the following:
    "claude-opus-4-6"

    Most intelligent model for building agents and coding

    "claude-sonnet-4-6"

    Frontier intelligence at scale — built for coding, agents, and enterprise workflows

    "claude-opus-4-5-20251101"

    Premium model combining maximum intelligence with practical performance

    "claude-opus-4-5"

    Premium model combining maximum intelligence with practical performance

    "claude-3-7-sonnet-latest"

    High-performance model with early extended thinking

    "claude-3-7-sonnet-20250219"

    High-performance model with early extended thinking

    "claude-3-5-haiku-latest"

    Fastest and most compact model for near-instant responsiveness

    "claude-3-5-haiku-20241022"

    Our fastest model

    "claude-haiku-4-5"

    Hybrid model, capable of near-instant responses and extended thinking

    "claude-haiku-4-5-20251001"

    Hybrid model, capable of near-instant responses and extended thinking

    "claude-sonnet-4-20250514"

    High-performance model with extended thinking

    "claude-sonnet-4-0"

    High-performance model with extended thinking

    "claude-4-sonnet-20250514"

    High-performance model with extended thinking

    "claude-sonnet-4-5"

    Our best model for real-world agents and coding

    "claude-sonnet-4-5-20250929"

    Our best model for real-world agents and coding

    "claude-opus-4-0"

    Our most capable model

    "claude-opus-4-20250514"

    Our most capable model

    "claude-4-opus-20250514"

    Our most capable model

    "claude-opus-4-1-20250805"

    Our most capable model

    "claude-3-opus-latest"

    Excels at writing and complex tasks

    "claude-3-opus-20240229"

    Excels at writing and complex tasks

    "claude-3-haiku-20240307"

    Our previous most fast and cost-effective

    str
    role: Literal["assistant"]

    Conversational role of the generated message.

    This will always be "assistant".

    stop_reason: Optional[StopReason]

    The reason that we stopped.

    This may be one the following values:

    • "end_turn": the model reached a natural stopping point
    • "max_tokens": we exceeded the requested max_tokens or the model's maximum
    • "stop_sequence": one of your provided custom stop_sequences was generated
    • "tool_use": the model invoked one or more tools
    • "pause_turn": we paused a long-running turn. You may provide the response back as-is in a subsequent request to let the model continue.
    • "refusal": when streaming classifiers intervene to handle potential policy violations

    In non-streaming mode this value is always non-null. In streaming mode, it is null in the message_start event and non-null otherwise.

    Accepts one of the following:
    "end_turn"
    "max_tokens"
    "stop_sequence"
    "tool_use"
    "pause_turn"
    "refusal"
    stop_sequence: Optional[str]

    Which custom stop sequence was generated, if any.

    This value will be a non-null string if one of your custom stop sequences was generated.

    type: Literal["message"]

    Object type.

    For Messages, this is always "message".

    usage: Usage

    Billing and rate-limit usage.

    Anthropic's API bills and rate-limits by token counts, as tokens represent the underlying cost to our systems.

    Under the hood, the API transforms requests into a format suitable for the model. The model's output then goes through a parsing stage before becoming an API response. As a result, the token counts in usage will not match one-to-one with the exact visible content of an API request or response.

    For example, output_tokens will be non-zero, even for an empty string response from Claude.

    Total input tokens in a request is the summation of input_tokens, cache_creation_input_tokens, and cache_read_input_tokens.

    cache_creation: Optional[CacheCreation]

    Breakdown of cached tokens by TTL

    ephemeral_1h_input_tokens: int

    The number of input tokens used to create the 1 hour cache entry.

    ephemeral_5m_input_tokens: int

    The number of input tokens used to create the 5 minute cache entry.

    cache_creation_input_tokens: Optional[int]

    The number of input tokens used to create the cache entry.

    cache_read_input_tokens: Optional[int]

    The number of input tokens read from the cache.

    inference_geo: Optional[str]

    The geographic region where inference was performed for this request.

    input_tokens: int

    The number of input tokens which were used.

    output_tokens: int

    The number of output tokens which were used.

    server_tool_use: Optional[ServerToolUsage]

    The number of server tool requests.

    web_fetch_requests: int

    The number of web fetch tool requests.

    web_search_requests: int

    The number of web search tool requests.

    service_tier: Optional[Literal["standard", "priority", "batch"]]

    If the request used the priority, standard, or batch tier.

    Accepts one of the following:
    "standard"
    "priority"
    "batch"
    type: Literal["succeeded"]
    class MessageBatchErroredResult: …
    error: ErrorResponse
    error: ErrorObject
    Accepts one of the following:
    class InvalidRequestError: …
    message: str
    type: Literal["invalid_request_error"]
    class AuthenticationError: …
    message: str
    type: Literal["authentication_error"]
    class BillingError: …
    message: str
    type: Literal["billing_error"]
    class PermissionError: …
    message: str
    type: Literal["permission_error"]
    class NotFoundError: …
    message: str
    type: Literal["not_found_error"]
    class RateLimitError: …
    message: str
    type: Literal["rate_limit_error"]
    class GatewayTimeoutError: …
    message: str
    type: Literal["timeout_error"]
    class APIErrorObject: …
    message: str
    type: Literal["api_error"]
    class OverloadedError: …
    message: str
    type: Literal["overloaded_error"]
    request_id: Optional[str]
    type: Literal["error"]
    type: Literal["errored"]
    class MessageBatchCanceledResult: …
    type: Literal["canceled"]
    class MessageBatchExpiredResult: …
    type: Literal["expired"]
    class MessageBatchSucceededResult: …
    message: Message
    id: str

    Unique object identifier.

    The format and length of IDs may change over time.

    container: Optional[Container]

    Information about the container used in the request (for the code execution tool)

    id: str

    Identifier for the container used in this request

    expires_at: datetime

    The time at which the container will expire.

    content: List[ContentBlock]

    Content generated by the model.

    This is an array of content blocks, each of which has a type that determines its shape.

    Example:

    [{"type": "text", "text": "Hi, I'm Claude."}]

    If the request input messages ended with an assistant turn, then the response content will continue directly from that last turn. You can use this to constrain the model's output.

    For example, if the input messages were:

    [
  {"role": "user", "content": "What's the Greek name for Sun? (A) Sol (B) Helios (C) Sun"},
  {"role": "assistant", "content": "The best answer is ("}
]

    Then the response content might be:

    [{"type": "text", "text": "B)"}]
    Accepts one of the following:
    class TextBlock: …
    citations: Optional[List[TextCitation]]

    Citations supporting the text block.

    The type of citation returned will depend on the type of document being cited. Citing a PDF results in page_location, plain text results in char_location, and content document results in content_block_location.

    Accepts one of the following:
    class CitationCharLocation: …
    cited_text: str
    document_index: int
    document_title: Optional[str]
    end_char_index: int
    file_id: Optional[str]
    start_char_index: int
    type: Literal["char_location"]
    class CitationPageLocation: …
    cited_text: str
    document_index: int
    document_title: Optional[str]
    end_page_number: int
    file_id: Optional[str]
    start_page_number: int
    type: Literal["page_location"]
    class CitationContentBlockLocation: …
    cited_text: str
    document_index: int
    document_title: Optional[str]
    end_block_index: int
    file_id: Optional[str]
    start_block_index: int
    type: Literal["content_block_location"]
    class CitationsWebSearchResultLocation: …
    cited_text: str
    encrypted_index: str
    title: Optional[str]
    type: Literal["web_search_result_location"]
    url: str
    class CitationsSearchResultLocation: …
    cited_text: str
    end_block_index: int
    search_result_index: int
    source: str
    start_block_index: int
    title: Optional[str]
    type: Literal["search_result_location"]
    text: str
    type: Literal["text"]
    class ThinkingBlock: …
    signature: str
    thinking: str
    type: Literal["thinking"]
    class RedactedThinkingBlock: …
    data: str
    type: Literal["redacted_thinking"]
    class ToolUseBlock: …
    id: str
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    input: Dict[str, object]
    name: str
    type: Literal["tool_use"]
    class ServerToolUseBlock: …
    id: str
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    input: Dict[str, object]
    name: Literal["web_search", "web_fetch", "code_execution", 4 more]
    Accepts one of the following:
    "web_search"
    "web_fetch"
    "code_execution"
    "bash_code_execution"
    "text_editor_code_execution"
    "tool_search_tool_regex"
    "tool_search_tool_bm25"
    type: Literal["server_tool_use"]
    class WebSearchToolResultBlock: …
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    content: WebSearchToolResultBlockContent
    Accepts one of the following:
    class WebSearchToolResultError: …
    error_code: WebSearchToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "max_uses_exceeded"
    "too_many_requests"
    "query_too_long"
    "request_too_large"
    type: Literal["web_search_tool_result_error"]
    List[WebSearchResultBlock]
    encrypted_content: str
    page_age: Optional[str]
    title: str
    type: Literal["web_search_result"]
    url: str
    tool_use_id: str
    type: Literal["web_search_tool_result"]
    class WebFetchToolResultBlock: …
    caller: Caller

    Tool invocation directly from the model.

    Accepts one of the following:
    class DirectCaller: …

    Tool invocation directly from the model.

    type: Literal["direct"]
    class ServerToolCaller: …

    Tool invocation generated by a server-side tool.

    tool_id: str
    type: Literal["code_execution_20250825"]
    class ServerToolCaller20260120: …
    tool_id: str
    type: Literal["code_execution_20260120"]
    content: Content
    Accepts one of the following:
    class WebFetchToolResultErrorBlock: …
    error_code: WebFetchToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "url_too_long"
    "url_not_allowed"
    "url_not_accessible"
    "unsupported_content_type"
    "too_many_requests"
    "max_uses_exceeded"
    "unavailable"
    type: Literal["web_fetch_tool_result_error"]
    class WebFetchBlock: …
    content: DocumentBlock
    citations: Optional[CitationsConfig]

    Citation configuration for the document

    enabled: bool
    source: Source
    Accepts one of the following:
    class Base64PDFSource: …
    data: str
    media_type: Literal["application/pdf"]
    type: Literal["base64"]
    class PlainTextSource: …
    data: str
    media_type: Literal["text/plain"]
    type: Literal["text"]
    title: Optional[str]

    The title of the document

    type: Literal["document"]
    retrieved_at: Optional[str]

    ISO 8601 timestamp when the content was retrieved

    type: Literal["web_fetch_result"]
    url: str

    Fetched content URL

    tool_use_id: str
    type: Literal["web_fetch_tool_result"]
    class CodeExecutionToolResultBlock: …
    content: CodeExecutionToolResultBlockContent

    Code execution result with encrypted stdout for PFC + web_search results.

    Accepts one of the following:
    class CodeExecutionToolResultError: …
    error_code: CodeExecutionToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    type: Literal["code_execution_tool_result_error"]
    class CodeExecutionResultBlock: …
    content: List[CodeExecutionOutputBlock]
    file_id: str
    type: Literal["code_execution_output"]
    return_code: int
    stderr: str
    stdout: str
    type: Literal["code_execution_result"]
    class EncryptedCodeExecutionResultBlock: …

    Code execution result with encrypted stdout for PFC + web_search results.

    content: List[CodeExecutionOutputBlock]
    file_id: str
    type: Literal["code_execution_output"]
    encrypted_stdout: str
    return_code: int
    stderr: str
    type: Literal["encrypted_code_execution_result"]
    tool_use_id: str
    type: Literal["code_execution_tool_result"]
    class BashCodeExecutionToolResultBlock: …
    content: Content
    Accepts one of the following:
    class BashCodeExecutionToolResultError: …
    error_code: BashCodeExecutionToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    "output_file_too_large"
    type: Literal["bash_code_execution_tool_result_error"]
    class BashCodeExecutionResultBlock: …
    content: List[BashCodeExecutionOutputBlock]
    file_id: str
    type: Literal["bash_code_execution_output"]
    return_code: int
    stderr: str
    stdout: str
    type: Literal["bash_code_execution_result"]
    tool_use_id: str
    type: Literal["bash_code_execution_tool_result"]
    class TextEditorCodeExecutionToolResultBlock: …
    content: Content
    Accepts one of the following:
    class TextEditorCodeExecutionToolResultError: …
    error_code: TextEditorCodeExecutionToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    "file_not_found"
    error_message: Optional[str]
    type: Literal["text_editor_code_execution_tool_result_error"]
    class TextEditorCodeExecutionViewResultBlock: …
    content: str
    file_type: Literal["text", "image", "pdf"]
    Accepts one of the following:
    "text"
    "image"
    "pdf"
    num_lines: Optional[int]
    start_line: Optional[int]
    total_lines: Optional[int]
    type: Literal["text_editor_code_execution_view_result"]
    class TextEditorCodeExecutionCreateResultBlock: …
    is_file_update: bool
    type: Literal["text_editor_code_execution_create_result"]
    class TextEditorCodeExecutionStrReplaceResultBlock: …
    lines: Optional[List[str]]
    new_lines: Optional[int]
    new_start: Optional[int]
    old_lines: Optional[int]
    old_start: Optional[int]
    type: Literal["text_editor_code_execution_str_replace_result"]
    tool_use_id: str
    type: Literal["text_editor_code_execution_tool_result"]
    class ToolSearchToolResultBlock: …
    content: Content
    Accepts one of the following:
    class ToolSearchToolResultError: …
    error_code: ToolSearchToolResultErrorCode
    Accepts one of the following:
    "invalid_tool_input"
    "unavailable"
    "too_many_requests"
    "execution_time_exceeded"
    error_message: Optional[str]
    type: Literal["tool_search_tool_result_error"]
    class ToolSearchToolSearchResultBlock: …
    tool_references: List[ToolReferenceBlock]
    tool_name: str
    type: Literal["tool_reference"]
    type: Literal["tool_search_tool_search_result"]
    tool_use_id: str
    type: Literal["tool_search_tool_result"]
    class ContainerUploadBlock: …

    Response model for a file uploaded to the container.

    file_id: str
    type: Literal["container_upload"]
    model: Model

    The model that will complete your prompt.

    See models for additional details and options.

    Accepts one of the following:
    Literal["claude-opus-4-6", "claude-sonnet-4-6", "claude-opus-4-5-20251101", 19 more]

    The model that will complete your prompt.

    See models for additional details and options.

    • claude-opus-4-6 - Most intelligent model for building agents and coding
    • claude-sonnet-4-6 - Frontier intelligence at scale — built for coding, agents, and enterprise workflows
    • claude-opus-4-5-20251101 - Premium model combining maximum intelligence with practical performance
    • claude-opus-4-5 - Premium model combining maximum intelligence with practical performance
    • claude-3-7-sonnet-latest - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-7-sonnet-20250219 - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-5-haiku-latest - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-5-haiku-20241022 - Deprecated: Will reach end-of-life on February 19th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-haiku-4-5 - Hybrid model, capable of near-instant responses and extended thinking
    • claude-haiku-4-5-20251001 - Hybrid model, capable of near-instant responses and extended thinking
    • claude-sonnet-4-20250514 - High-performance model with extended thinking
    • claude-sonnet-4-0 - High-performance model with extended thinking
    • claude-4-sonnet-20250514 - High-performance model with extended thinking
    • claude-sonnet-4-5 - Our best model for real-world agents and coding
    • claude-sonnet-4-5-20250929 - Our best model for real-world agents and coding
    • claude-opus-4-0 - Our most capable model
    • claude-opus-4-20250514 - Our most capable model
    • claude-4-opus-20250514 - Our most capable model
    • claude-opus-4-1-20250805 - Our most capable model
    • claude-3-opus-latest - Deprecated: Will reach end-of-life on January 5th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-opus-20240229 - Deprecated: Will reach end-of-life on January 5th, 2026. Please migrate to a newer model. Visit https://docs.anthropic.com/en/docs/resources/model-deprecations for more information.
    • claude-3-haiku-20240307 - Our previous most fast and cost-effective
    Accepts one of the following:
    "claude-opus-4-6"

    Most intelligent model for building agents and coding

    "claude-sonnet-4-6"

    Frontier intelligence at scale — built for coding, agents, and enterprise workflows

    "claude-opus-4-5-20251101"

    Premium model combining maximum intelligence with practical performance

    "claude-opus-4-5"

    Premium model combining maximum intelligence with practical performance

    "claude-3-7-sonnet-latest"

    High-performance model with early extended thinking

    "claude-3-7-sonnet-20250219"

    High-performance model with early extended thinking

    "claude-3-5-haiku-latest"

    Fastest and most compact model for near-instant responsiveness

    "claude-3-5-haiku-20241022"

    Our fastest model

    "claude-haiku-4-5"

    Hybrid model, capable of near-instant responses and extended thinking

    "claude-haiku-4-5-20251001"

    Hybrid model, capable of near-instant responses and extended thinking

    "claude-sonnet-4-20250514"

    High-performance model with extended thinking

    "claude-sonnet-4-0"

    High-performance model with extended thinking

    "claude-4-sonnet-20250514"

    High-performance model with extended thinking

    "claude-sonnet-4-5"

    Our best model for real-world agents and coding

    "claude-sonnet-4-5-20250929"

    Our best model for real-world agents and coding

    "claude-opus-4-0"

    Our most capable model

    "claude-opus-4-20250514"

    Our most capable model

    "claude-4-opus-20250514"

    Our most capable model

    "claude-opus-4-1-20250805"

    Our most capable model

    "claude-3-opus-latest"

    Excels at writing and complex tasks

    "claude-3-opus-20240229"

    Excels at writing and complex tasks

    "claude-3-haiku-20240307"

    Our previous most fast and cost-effective

    str
    role: Literal["assistant"]

    Conversational role of the generated message.

    This will always be "assistant".

    stop_reason: Optional[StopReason]

    The reason that we stopped.

    This may be one the following values:

    • "end_turn": the model reached a natural stopping point
    • "max_tokens": we exceeded the requested max_tokens or the model's maximum
    • "stop_sequence": one of your provided custom stop_sequences was generated
    • "tool_use": the model invoked one or more tools
    • "pause_turn": we paused a long-running turn. You may provide the response back as-is in a subsequent request to let the model continue.
    • "refusal": when streaming classifiers intervene to handle potential policy violations

    In non-streaming mode this value is always non-null. In streaming mode, it is null in the message_start event and non-null otherwise.

    Accepts one of the following:
    "end_turn"
    "max_tokens"
    "stop_sequence"
    "tool_use"
    "pause_turn"
    "refusal"
    stop_sequence: Optional[str]

    Which custom stop sequence was generated, if any.

    This value will be a non-null string if one of your custom stop sequences was generated.

    type: Literal["message"]

    Object type.

    For Messages, this is always "message".

    usage: Usage

    Billing and rate-limit usage.

    Anthropic's API bills and rate-limits by token counts, as tokens represent the underlying cost to our systems.

    Under the hood, the API transforms requests into a format suitable for the model. The model's output then goes through a parsing stage before becoming an API response. As a result, the token counts in usage will not match one-to-one with the exact visible content of an API request or response.

    For example, output_tokens will be non-zero, even for an empty string response from Claude.

    Total input tokens in a request is the summation of input_tokens, cache_creation_input_tokens, and cache_read_input_tokens.

    cache_creation: Optional[CacheCreation]

    Breakdown of cached tokens by TTL

    ephemeral_1h_input_tokens: int

    The number of input tokens used to create the 1 hour cache entry.

    ephemeral_5m_input_tokens: int

    The number of input tokens used to create the 5 minute cache entry.

    cache_creation_input_tokens: Optional[int]

    The number of input tokens used to create the cache entry.

    cache_read_input_tokens: Optional[int]

    The number of input tokens read from the cache.

    inference_geo: Optional[str]

    The geographic region where inference was performed for this request.

    input_tokens: int

    The number of input tokens which were used.

    output_tokens: int

    The number of output tokens which were used.

    server_tool_use: Optional[ServerToolUsage]

    The number of server tool requests.

    web_fetch_requests: int

    The number of web fetch tool requests.

    web_search_requests: int

    The number of web search tool requests.

    service_tier: Optional[Literal["standard", "priority", "batch"]]

    If the request used the priority, standard, or batch tier.

    Accepts one of the following:
    "standard"
    "priority"
    "batch"
    type: Literal["succeeded"]

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