Create a Message
Send a structured list of input messages with text and/or image content, and the model will generate the next message in the conversation.
The Messages API can be used for either single queries or stateless multi-turn conversations.
Learn more about the Messages API in our user guide
ParametersExpand Collapse
params BetaMessageNewParams
Body param: The maximum number of tokens to generate before stopping.
Note that our models may stop before reaching this maximum. This parameter only specifies the absolute maximum number of tokens to generate.
Different models have different maximum values for this parameter. See models for details.
Messages param.Field[[]BetaMessageParamResp]Body param: Input messages.
Our models are trained to operate on alternating user and assistant conversational turns. When creating a new Message, you specify the prior conversational turns with the messages parameter, and the model then generates the next Message in the conversation. Consecutive user or assistant turns in your request will be combined into a single turn.
Each input message must be an object with a role and content. You can specify a single user-role message, or you can include multiple user and assistant messages.
If the final message uses the assistant role, the response content will continue immediately from the content in that message. This can be used to constrain part of the model's response.
Example with a single user message:
[{"role": "user", "content": "Hello, Claude"}]
Example with multiple conversational turns:
[
{"role": "user", "content": "Hello there."},
{"role": "assistant", "content": "Hi, I'm Claude. How can I help you?"},
{"role": "user", "content": "Can you explain LLMs in plain English?"},
]
Example with a partially-filled response from Claude:
[
{"role": "user", "content": "What's the Greek name for Sun? (A) Sol (B) Helios (C) Sun"},
{"role": "assistant", "content": "The best answer is ("},
]
Each input message content may be either a single string or an array of content blocks, where each block has a specific type. Using a string for content is shorthand for an array of one content block of type "text". The following input messages are equivalent:
{"role": "user", "content": "Hello, Claude"}
{"role": "user", "content": [{"type": "text", "text": "Hello, Claude"}]}
See input examples.
Note that if you want to include a system prompt, you can use the top-level system parameter — there is no "system" role for input messages in the Messages API.
There is a limit of 100,000 messages in a single request.
Body param: Input messages.
Our models are trained to operate on alternating user and assistant conversational turns. When creating a new Message, you specify the prior conversational turns with the messages parameter, and the model then generates the next Message in the conversation. Consecutive user or assistant turns in your request will be combined into a single turn.
Each input message must be an object with a role and content. You can specify a single user-role message, or you can include multiple user and assistant messages.
If the final message uses the assistant role, the response content will continue immediately from the content in that message. This can be used to constrain part of the model's response.
Example with a single user message:
[{"role": "user", "content": "Hello, Claude"}]
Example with multiple conversational turns:
[
{"role": "user", "content": "Hello there."},
{"role": "assistant", "content": "Hi, I'm Claude. How can I help you?"},
{"role": "user", "content": "Can you explain LLMs in plain English?"},
]
Example with a partially-filled response from Claude:
[
{"role": "user", "content": "What's the Greek name for Sun? (A) Sol (B) Helios (C) Sun"},
{"role": "assistant", "content": "The best answer is ("},
]
Each input message content may be either a single string or an array of content blocks, where each block has a specific type. Using a string for content is shorthand for an array of one content block of type "text". The following input messages are equivalent:
{"role": "user", "content": "Hello, Claude"}
{"role": "user", "content": [{"type": "text", "text": "Hello, Claude"}]}
See input examples.
Note that if you want to include a system prompt, you can use the top-level system parameter — there is no "system" role for input messages in the Messages API.
There is a limit of 100,000 messages in a single request.
Content []BetaContentBlockParamUnionResp
type BetaTextBlockParamResp struct{…}
Type Text
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCitationCharLocationParamResp struct{…}
Type CharLocation
type BetaCitationPageLocationParamResp struct{…}
Type PageLocation
type BetaCitationContentBlockLocationParamResp struct{…}
Type ContentBlockLocation
type BetaCitationWebSearchResultLocationParamResp struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocationParamResp struct{…}
Type SearchResultLocation
type BetaImageBlockParamResp struct{…}
Source BetaImageBlockParamSourceUnionResp
type BetaBase64ImageSource struct{…}
MediaType BetaBase64ImageSourceMediaType
Type Base64
type BetaURLImageSource struct{…}
Type URL
type BetaFileImageSource struct{…}
Type File
Type Image
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaRequestDocumentBlock struct{…}
Source BetaRequestDocumentBlockSourceUnion
type BetaBase64PDFSource struct{…}
MediaType ApplicationPDF
Type Base64
type BetaPlainTextSource struct{…}
MediaType TextPlain
Type Text
type BetaContentBlockSource struct{…}
Content BetaContentBlockSourceContentUnion
type BetaTextBlockParamResp struct{…}
Type Text
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCitationCharLocationParamResp struct{…}
Type CharLocation
type BetaCitationPageLocationParamResp struct{…}
Type PageLocation
type BetaCitationContentBlockLocationParamResp struct{…}
Type ContentBlockLocation
type BetaCitationWebSearchResultLocationParamResp struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocationParamResp struct{…}
Type SearchResultLocation
type BetaImageBlockParamResp struct{…}
Source BetaImageBlockParamSourceUnionResp
type BetaBase64ImageSource struct{…}
MediaType BetaBase64ImageSourceMediaType
Type Base64
type BetaURLImageSource struct{…}
Type URL
type BetaFileImageSource struct{…}
Type File
Type Image
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Type Content
type BetaURLPDFSource struct{…}
Type URL
type BetaFileDocumentSource struct{…}
Type File
Type Document
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaSearchResultBlockParamResp struct{…}
Content []BetaTextBlockParamResp
Type Text
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCitationCharLocationParamResp struct{…}
Type CharLocation
type BetaCitationPageLocationParamResp struct{…}
Type PageLocation
type BetaCitationContentBlockLocationParamResp struct{…}
Type ContentBlockLocation
type BetaCitationWebSearchResultLocationParamResp struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocationParamResp struct{…}
Type SearchResultLocation
Type SearchResult
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaThinkingBlockParamResp struct{…}
Type Thinking
type BetaRedactedThinkingBlockParamResp struct{…}
Type RedactedThinking
type BetaToolUseBlockParamResp struct{…}
Type ToolUse
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaToolResultBlockParamResp struct{…}
Type ToolResult
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Content []BetaToolResultBlockParamContentUnionRespoptional
[]BetaToolResultBlockParamContentUnionResp
type BetaTextBlockParamResp struct{…}
Type Text
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCitationCharLocationParamResp struct{…}
Type CharLocation
type BetaCitationPageLocationParamResp struct{…}
Type PageLocation
type BetaCitationContentBlockLocationParamResp struct{…}
Type ContentBlockLocation
type BetaCitationWebSearchResultLocationParamResp struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocationParamResp struct{…}
Type SearchResultLocation
type BetaImageBlockParamResp struct{…}
Source BetaImageBlockParamSourceUnionResp
type BetaBase64ImageSource struct{…}
MediaType BetaBase64ImageSourceMediaType
Type Base64
type BetaURLImageSource struct{…}
Type URL
type BetaFileImageSource struct{…}
Type File
Type Image
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaSearchResultBlockParamResp struct{…}
Content []BetaTextBlockParamResp
Type Text
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCitationCharLocationParamResp struct{…}
Type CharLocation
type BetaCitationPageLocationParamResp struct{…}
Type PageLocation
type BetaCitationContentBlockLocationParamResp struct{…}
Type ContentBlockLocation
type BetaCitationWebSearchResultLocationParamResp struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocationParamResp struct{…}
Type SearchResultLocation
Type SearchResult
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaRequestDocumentBlock struct{…}
Source BetaRequestDocumentBlockSourceUnion
type BetaBase64PDFSource struct{…}
MediaType ApplicationPDF
Type Base64
type BetaPlainTextSource struct{…}
MediaType TextPlain
Type Text
type BetaContentBlockSource struct{…}
Content BetaContentBlockSourceContentUnion
type BetaTextBlockParamResp struct{…}
Type Text
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCitationCharLocationParamResp struct{…}
Type CharLocation
type BetaCitationPageLocationParamResp struct{…}
Type PageLocation
type BetaCitationContentBlockLocationParamResp struct{…}
Type ContentBlockLocation
type BetaCitationWebSearchResultLocationParamResp struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocationParamResp struct{…}
Type SearchResultLocation
type BetaImageBlockParamResp struct{…}
Source BetaImageBlockParamSourceUnionResp
type BetaBase64ImageSource struct{…}
MediaType BetaBase64ImageSourceMediaType
Type Base64
type BetaURLImageSource struct{…}
Type URL
type BetaFileImageSource struct{…}
Type File
Type Image
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Type Content
type BetaURLPDFSource struct{…}
Type URL
type BetaFileDocumentSource struct{…}
Type File
Type Document
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaServerToolUseBlockParamResp struct{…}
Name BetaServerToolUseBlockParamName
Type ServerToolUse
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaWebSearchToolResultBlockParamResp struct{…}
Type WebSearchResult
type BetaWebSearchToolRequestError struct{…}
ErrorCode BetaWebSearchToolResultErrorCode
Type WebSearchToolResultError
Type WebSearchToolResult
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaWebFetchToolResultBlockParamResp struct{…}
Content BetaWebFetchToolResultBlockParamContentUnionResp
type BetaWebFetchToolResultErrorBlockParamResp struct{…}
ErrorCode BetaWebFetchToolResultErrorCode
Type WebFetchToolResultError
type BetaWebFetchBlockParamResp struct{…}
Content BetaRequestDocumentBlock
Source BetaRequestDocumentBlockSourceUnion
type BetaBase64PDFSource struct{…}
MediaType ApplicationPDF
Type Base64
type BetaPlainTextSource struct{…}
MediaType TextPlain
Type Text
type BetaContentBlockSource struct{…}
Content BetaContentBlockSourceContentUnion
type BetaTextBlockParamResp struct{…}
Type Text
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCitationCharLocationParamResp struct{…}
Type CharLocation
type BetaCitationPageLocationParamResp struct{…}
Type PageLocation
type BetaCitationContentBlockLocationParamResp struct{…}
Type ContentBlockLocation
type BetaCitationWebSearchResultLocationParamResp struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocationParamResp struct{…}
Type SearchResultLocation
type BetaImageBlockParamResp struct{…}
Source BetaImageBlockParamSourceUnionResp
type BetaBase64ImageSource struct{…}
MediaType BetaBase64ImageSourceMediaType
Type Base64
type BetaURLImageSource struct{…}
Type URL
type BetaFileImageSource struct{…}
Type File
Type Image
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Type Content
type BetaURLPDFSource struct{…}
Type URL
type BetaFileDocumentSource struct{…}
Type File
Type Document
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Type WebFetchResult
Fetched content URL
ISO 8601 timestamp when the content was retrieved
Type WebFetchToolResult
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCodeExecutionToolResultBlockParamResp struct{…}
type BetaCodeExecutionToolResultErrorParamResp struct{…}
ErrorCode BetaCodeExecutionToolResultErrorCode
Type CodeExecutionToolResultError
type BetaCodeExecutionResultBlockParamResp struct{…}
Content []BetaCodeExecutionOutputBlockParamResp
Type CodeExecutionOutput
Type CodeExecutionResult
Type CodeExecutionToolResult
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaBashCodeExecutionToolResultBlockParamResp struct{…}
Content BetaBashCodeExecutionToolResultBlockParamContentUnionResp
type BetaBashCodeExecutionToolResultErrorParamResp struct{…}
ErrorCode BetaBashCodeExecutionToolResultErrorParamErrorCode
Type BashCodeExecutionToolResultError
type BetaBashCodeExecutionResultBlockParamResp struct{…}
Type BashCodeExecutionOutput
Type BashCodeExecutionResult
Type BashCodeExecutionToolResult
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaTextEditorCodeExecutionToolResultBlockParamResp struct{…}
Content BetaTextEditorCodeExecutionToolResultBlockParamContentUnionResp
type BetaTextEditorCodeExecutionToolResultErrorParamResp struct{…}
ErrorCode BetaTextEditorCodeExecutionToolResultErrorParamErrorCode
Type TextEditorCodeExecutionToolResultError
type BetaTextEditorCodeExecutionViewResultBlockParamResp struct{…}
FileType BetaTextEditorCodeExecutionViewResultBlockParamFileType
Type TextEditorCodeExecutionViewResult
type BetaTextEditorCodeExecutionCreateResultBlockParamResp struct{…}
Type TextEditorCodeExecutionCreateResult
type BetaTextEditorCodeExecutionStrReplaceResultBlockParamResp struct{…}
Type TextEditorCodeExecutionStrReplaceResult
Type TextEditorCodeExecutionToolResult
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaMCPToolUseBlockParamResp struct{…}
The name of the MCP server
Type MCPToolUse
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaRequestMCPToolResultBlockParamResp struct{…}
Type MCPToolResult
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Content BetaRequestMCPToolResultBlockParamContentUnionRespoptional
Type Text
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCitationCharLocationParamResp struct{…}
Type CharLocation
type BetaCitationPageLocationParamResp struct{…}
Type PageLocation
type BetaCitationContentBlockLocationParamResp struct{…}
Type ContentBlockLocation
type BetaCitationWebSearchResultLocationParamResp struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocationParamResp struct{…}
Type SearchResultLocation
type BetaContainerUploadBlockParamResp struct{…}A content block that represents a file to be uploaded to the container
Files uploaded via this block will be available in the container's input directory.
A content block that represents a file to be uploaded to the container Files uploaded via this block will be available in the container's input directory.
Type ContainerUpload
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Role BetaMessageParamRole
Body param: The model that will complete your prompt.
See models for additional details and options.
Body param: Container identifier for reuse across requests.
Body param: Container identifier for reuse across requests.
type BetaContainerParamsResp struct{…}Container parameters with skills to be loaded.
Container parameters with skills to be loaded.
Container id
List of skills to load in the container
List of skills to load in the container
Skill ID
Type BetaSkillParamsTypeType of skill - either 'anthropic' (built-in) or 'custom' (user-defined)
Type of skill - either 'anthropic' (built-in) or 'custom' (user-defined)
Skill version or 'latest' for most recent version
Body param: Context management configuration.
This allows you to control how Claude manages context across multiple requests, such as whether to clear function results or not.
Body param: MCP servers to be utilized in this request
Body param: MCP servers to be utilized in this request
Type URL
Body param: An object describing metadata about the request.
Body param: Determines whether to use priority capacity (if available) or standard capacity for this request.
Anthropic offers different levels of service for your API requests. See service-tiers for details.
Body param: Determines whether to use priority capacity (if available) or standard capacity for this request.
Anthropic offers different levels of service for your API requests. See service-tiers for details.
Body param: Custom text sequences that will cause the model to stop generating.
Our models will normally stop when they have naturally completed their turn, which will result in a response stop_reason of "end_turn".
If you want the model to stop generating when it encounters custom strings of text, you can use the stop_sequences parameter. If the model encounters one of the custom sequences, the response stop_reason value will be "stop_sequence" and the response stop_sequence value will contain the matched stop sequence.
Body param: System prompt.
A system prompt is a way of providing context and instructions to Claude, such as specifying a particular goal or role. See our guide to system prompts.
Body param: System prompt.
A system prompt is a way of providing context and instructions to Claude, such as specifying a particular goal or role. See our guide to system prompts.
Type Text
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCitationCharLocationParamResp struct{…}
Type CharLocation
type BetaCitationPageLocationParamResp struct{…}
Type PageLocation
type BetaCitationContentBlockLocationParamResp struct{…}
Type ContentBlockLocation
type BetaCitationWebSearchResultLocationParamResp struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocationParamResp struct{…}
Type SearchResultLocation
Body param: Amount of randomness injected into the response.
Defaults to 1.0. Ranges from 0.0 to 1.0. Use temperature closer to 0.0 for analytical / multiple choice, and closer to 1.0 for creative and generative tasks.
Note that even with temperature of 0.0, the results will not be fully deterministic.
Body param: Configuration for enabling Claude's extended thinking.
When enabled, responses include thinking content blocks showing Claude's thinking process before the final answer. Requires a minimum budget of 1,024 tokens and counts towards your max_tokens limit.
See extended thinking for details.
Body param: How the model should use the provided tools. The model can use a specific tool, any available tool, decide by itself, or not use tools at all.
Body param: Definitions of tools that the model may use.
If you include tools in your API request, the model may return tool_use content blocks that represent the model's use of those tools. You can then run those tools using the tool input generated by the model and then optionally return results back to the model using tool_result content blocks.
There are two types of tools: client tools and server tools. The behavior described below applies to client tools. For server tools, see their individual documentation as each has its own behavior (e.g., the web search tool).
Each tool definition includes:
name: Name of the tool.description: Optional, but strongly-recommended description of the tool.input_schema: JSON schema for the tool input shape that the model will produce in tool_use output content blocks.
For example, if you defined tools as:
[
{
"name": "get_stock_price",
"description": "Get the current stock price for a given ticker symbol.",
"input_schema": {
"type": "object",
"properties": {
"ticker": {
"type": "string",
"description": "The stock ticker symbol, e.g. AAPL for Apple Inc."
}
},
"required": ["ticker"]
}
}
]
And then asked the model "What's the S&P 500 at today?", the model might produce tool_use content blocks in the response like this:
[
{
"type": "tool_use",
"id": "toolu_01D7FLrfh4GYq7yT1ULFeyMV",
"name": "get_stock_price",
"input": { "ticker": "^GSPC" }
}
]
You might then run your get_stock_price tool with {"ticker": "^GSPC"} as an input, and return the following back to the model in a subsequent user message:
[
{
"type": "tool_result",
"tool_use_id": "toolu_01D7FLrfh4GYq7yT1ULFeyMV",
"content": "259.75 USD"
}
]
Tools can be used for workflows that include running client-side tools and functions, or more generally whenever you want the model to produce a particular JSON structure of output.
See our guide for more details.
Body param: Definitions of tools that the model may use.
If you include tools in your API request, the model may return tool_use content blocks that represent the model's use of those tools. You can then run those tools using the tool input generated by the model and then optionally return results back to the model using tool_result content blocks.
There are two types of tools: client tools and server tools. The behavior described below applies to client tools. For server tools, see their individual documentation as each has its own behavior (e.g., the web search tool).
Each tool definition includes:
name: Name of the tool.description: Optional, but strongly-recommended description of the tool.input_schema: JSON schema for the toolinputshape that the model will produce intool_useoutput content blocks.
For example, if you defined tools as:
[
{
"name": "get_stock_price",
"description": "Get the current stock price for a given ticker symbol.",
"input_schema": {
"type": "object",
"properties": {
"ticker": {
"type": "string",
"description": "The stock ticker symbol, e.g. AAPL for Apple Inc."
}
},
"required": ["ticker"]
}
}
]
And then asked the model "What's the S&P 500 at today?", the model might produce tool_use content blocks in the response like this:
[
{
"type": "tool_use",
"id": "toolu_01D7FLrfh4GYq7yT1ULFeyMV",
"name": "get_stock_price",
"input": { "ticker": "^GSPC" }
}
]
You might then run your get_stock_price tool with {"ticker": "^GSPC"} as an input, and return the following back to the model in a subsequent user message:
[
{
"type": "tool_result",
"tool_use_id": "toolu_01D7FLrfh4GYq7yT1ULFeyMV",
"content": "259.75 USD"
}
]
Tools can be used for workflows that include running client-side tools and functions, or more generally whenever you want the model to produce a particular JSON structure of output.
See our guide for more details.
type BetaTool struct{…}
InputSchema BetaToolInputSchemaJSON schema for this tool's input.
This defines the shape of the input that your tool accepts and that the model will produce.
JSON schema for this tool's input.
This defines the shape of the input that your tool accepts and that the model will produce.
Type Object
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Description of what this tool does.
Tool descriptions should be as detailed as possible. The more information that the model has about what the tool is and how to use it, the better it will perform. You can use natural language descriptions to reinforce important aspects of the tool input JSON schema.
Type BetaToolTypeoptional
type BetaToolBash20241022 struct{…}
Name BashName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type Bash20241022
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaToolBash20250124 struct{…}
Name BashName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type Bash20250124
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCodeExecutionTool20250522 struct{…}
Name CodeExecutionName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type CodeExecution20250522
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaCodeExecutionTool20250825 struct{…}
Name CodeExecutionName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type CodeExecution20250825
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaToolComputerUse20241022 struct{…}
The height of the display in pixels.
The width of the display in pixels.
Name ComputerName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type Computer20241022
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The X11 display number (e.g. 0, 1) for the display.
type BetaMemoryTool20250818 struct{…}
Name MemoryName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type Memory20250818
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaToolComputerUse20250124 struct{…}
The height of the display in pixels.
The width of the display in pixels.
Name ComputerName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type Computer20250124
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The X11 display number (e.g. 0, 1) for the display.
type BetaToolTextEditor20241022 struct{…}
Name StrReplaceEditorName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type TextEditor20241022
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaToolTextEditor20250124 struct{…}
Name StrReplaceEditorName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type TextEditor20250124
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaToolTextEditor20250429 struct{…}
Name StrReplaceBasedEditToolName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type TextEditor20250429
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
type BetaToolTextEditor20250728 struct{…}
Name StrReplaceBasedEditToolName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type TextEditor20250728
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Maximum number of characters to display when viewing a file. If not specified, defaults to displaying the full file.
type BetaWebSearchTool20250305 struct{…}
Name WebSearchName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type WebSearch20250305
If provided, only these domains will be included in results. Cannot be used alongside blocked_domains.
If provided, these domains will never appear in results. Cannot be used alongside allowed_domains.
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Maximum number of times the tool can be used in the API request.
UserLocation BetaWebSearchTool20250305UserLocationoptionalParameters for the user's location. Used to provide more relevant search results.
Parameters for the user's location. Used to provide more relevant search results.
Type Approximate
The city of the user.
The region of the user.
type BetaWebFetchTool20250910 struct{…}
Name WebFetchName of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Name of the tool.
This is how the tool will be called by the model and in tool_use blocks.
Type WebFetch20250910
List of domains to allow fetching from
List of domains to block fetching from
Create a cache control breakpoint at this content block.
Create a cache control breakpoint at this content block.
Type Ephemeral
TTL BetaCacheControlEphemeralTTLoptionalThe time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
The time-to-live for the cache control breakpoint.
This may be one the following values:
5m: 5 minutes1h: 1 hour
Defaults to 5m.
Citations configuration for fetched documents. Citations are disabled by default.
Citations configuration for fetched documents. Citations are disabled by default.
Maximum number of tokens used by including web page text content in the context. The limit is approximate and does not apply to binary content such as PDFs.
Maximum number of times the tool can be used in the API request.
Body param: Only sample from the top K options for each subsequent token.
Used to remove "long tail" low probability responses. Learn more technical details here.
Recommended for advanced use cases only. You usually only need to use temperature.
Body param: Use nucleus sampling.
In nucleus sampling, we compute the cumulative distribution over all the options for each subsequent token in decreasing probability order and cut it off once it reaches a particular probability specified by top_p. You should either alter temperature or top_p, but not both.
Recommended for advanced use cases only. You usually only need to use temperature.
Betas param.Field[[]AnthropicBeta]optionalHeader param: Optional header to specify the beta version(s) you want to use.
Header param: Optional header to specify the beta version(s) you want to use.
type AnthropicBeta string
ReturnsExpand Collapse
type BetaMessage struct{…}
Unique object identifier.
The format and length of IDs may change over time.
Container BetaContainerInformation about the container used in the request (for the code execution tool)
Information about the container used in the request (for the code execution tool)
Identifier for the container used in this request
The time at which the container will expire.
Skills []BetaSkillSkills loaded in the container
Skills loaded in the container
Skill ID
Type BetaSkillTypeType of skill - either 'anthropic' (built-in) or 'custom' (user-defined)
Type of skill - either 'anthropic' (built-in) or 'custom' (user-defined)
Skill version or 'latest' for most recent version
Content []BetaContentBlockUnionContent 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)"}]
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)"}]
type BetaTextBlock struct{…}
Citations []BetaTextCitationUnionCitations 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.
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.
type BetaCitationCharLocation struct{…}
Type CharLocation
type BetaCitationPageLocation struct{…}
Type PageLocation
type BetaCitationContentBlockLocation struct{…}
Type ContentBlockLocation
type BetaCitationsWebSearchResultLocation struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocation struct{…}
Type SearchResultLocation
Type Text
type BetaThinkingBlock struct{…}
Type Thinking
type BetaRedactedThinkingBlock struct{…}
Type RedactedThinking
type BetaToolUseBlock struct{…}
Type ToolUse
type BetaServerToolUseBlock struct{…}
Name BetaServerToolUseBlockName
Type ServerToolUse
type BetaWebSearchToolResultBlock struct{…}
type BetaWebSearchToolResultError struct{…}
ErrorCode BetaWebSearchToolResultErrorCode
Type WebSearchToolResultError
Type WebSearchResult
Type WebSearchToolResult
type BetaWebFetchToolResultBlock struct{…}
Content BetaWebFetchToolResultBlockContentUnion
type BetaWebFetchToolResultErrorBlock struct{…}
ErrorCode BetaWebFetchToolResultErrorCode
Type WebFetchToolResultError
type BetaWebFetchBlock struct{…}
Content BetaDocumentBlock
Citations BetaCitationConfigCitation configuration for the document
Citation configuration for the document
Source BetaDocumentBlockSourceUnion
type BetaBase64PDFSource struct{…}
MediaType ApplicationPDF
Type Base64
type BetaPlainTextSource struct{…}
MediaType TextPlain
Type Text
The title of the document
Type Document
ISO 8601 timestamp when the content was retrieved
Type WebFetchResult
Fetched content URL
Type WebFetchToolResult
type BetaCodeExecutionToolResultBlock struct{…}
type BetaCodeExecutionToolResultError struct{…}
ErrorCode BetaCodeExecutionToolResultErrorCode
Type CodeExecutionToolResultError
type BetaCodeExecutionResultBlock struct{…}
Content []BetaCodeExecutionOutputBlock
Type CodeExecutionOutput
Type CodeExecutionResult
Type CodeExecutionToolResult
type BetaBashCodeExecutionToolResultBlock struct{…}
Content BetaBashCodeExecutionToolResultBlockContentUnion
type BetaBashCodeExecutionToolResultError struct{…}
ErrorCode BetaBashCodeExecutionToolResultErrorErrorCode
Type BashCodeExecutionToolResultError
type BetaBashCodeExecutionResultBlock struct{…}
Content []BetaBashCodeExecutionOutputBlock
Type BashCodeExecutionOutput
Type BashCodeExecutionResult
Type BashCodeExecutionToolResult
type BetaTextEditorCodeExecutionToolResultBlock struct{…}
Content BetaTextEditorCodeExecutionToolResultBlockContentUnion
type BetaTextEditorCodeExecutionToolResultError struct{…}
ErrorCode BetaTextEditorCodeExecutionToolResultErrorErrorCode
Type TextEditorCodeExecutionToolResultError
type BetaTextEditorCodeExecutionViewResultBlock struct{…}
FileType BetaTextEditorCodeExecutionViewResultBlockFileType
Type TextEditorCodeExecutionViewResult
type BetaTextEditorCodeExecutionCreateResultBlock struct{…}
Type TextEditorCodeExecutionCreateResult
type BetaTextEditorCodeExecutionStrReplaceResultBlock struct{…}
Type TextEditorCodeExecutionStrReplaceResult
Type TextEditorCodeExecutionToolResult
type BetaMCPToolUseBlock struct{…}
The name of the MCP tool
The name of the MCP server
Type MCPToolUse
type BetaMCPToolResultBlock struct{…}
Content BetaMCPToolResultBlockContentUnion
Citations []BetaTextCitationUnionCitations 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.
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.
type BetaCitationCharLocation struct{…}
Type CharLocation
type BetaCitationPageLocation struct{…}
Type PageLocation
type BetaCitationContentBlockLocation struct{…}
Type ContentBlockLocation
type BetaCitationsWebSearchResultLocation struct{…}
Type WebSearchResultLocation
type BetaCitationSearchResultLocation struct{…}
Type SearchResultLocation
Type Text
Type MCPToolResult
type BetaContainerUploadBlock struct{…}Response model for a file uploaded to the container.
Response model for a file uploaded to the container.
Type ContainerUpload
ContextManagement BetaContextManagementResponseContext management response.
Information about context management strategies applied during the request.
Context management response.
Information about context management strategies applied during the request.
AppliedEdits []BetaContextManagementResponseAppliedEditUnionList of context management edits that were applied.
List of context management edits that were applied.
type BetaClearToolUses20250919EditResponse struct{…}
Number of input tokens cleared by this edit.
Number of tool uses that were cleared.
Type ClearToolUses20250919The type of context management edit applied.
The type of context management edit applied.
type BetaClearThinking20251015EditResponse struct{…}
Number of input tokens cleared by this edit.
Number of thinking turns that were cleared.
Type ClearThinking20251015The type of context management edit applied.
The type of context management edit applied.
Model ModelThe model that will complete your prompt.
See models for additional details and options.
The model that will complete your prompt.
See models for additional details and options.
type Model stringThe model that will complete your prompt.
See models for additional details and options.
The model that will complete your prompt.
See models for additional details and options.
High-performance model with early extended thinking
High-performance model with early extended thinking
Fastest and most compact model for near-instant responsiveness
Our fastest model
Hybrid model, capable of near-instant responses and extended thinking
Hybrid model, capable of near-instant responses and extended thinking
High-performance model with extended thinking
High-performance model with extended thinking
High-performance model with extended thinking
Our best model for real-world agents and coding
Our best model for real-world agents and coding
Our most capable model
Our most capable model
Our most capable model
Our most capable model
Excels at writing and complex tasks
Excels at writing and complex tasks
Our previous most fast and cost-effective
Role AssistantConversational role of the generated message.
This will always be "assistant".
Conversational role of the generated message.
This will always be "assistant".
StopReason BetaStopReasonThe 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.
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 requestedmax_tokensor the model's maximum"stop_sequence": one of your provided customstop_sequenceswas 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.
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 MessageObject type.
For Messages, this is always "message".
Object type.
For Messages, this is always "message".
Usage BetaUsageBilling 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.
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.
CacheCreation BetaCacheCreationBreakdown of cached tokens by TTL
Breakdown of cached tokens by TTL
The number of input tokens used to create the 1 hour cache entry.
The number of input tokens used to create the 5 minute cache entry.
The number of input tokens used to create the cache entry.
The number of input tokens read from the cache.
The number of input tokens which were used.
The number of output tokens which were used.
ServerToolUse BetaServerToolUsageThe number of server tool requests.
The number of server tool requests.
The number of web fetch tool requests.
The number of web search tool requests.
ServiceTier BetaUsageServiceTierIf the request used the priority, standard, or batch tier.
If the request used the priority, standard, or batch tier.
Create a Message
package main
import (
"context"
"fmt"
"github.com/anthropics/anthropic-sdk-go"
"github.com/anthropics/anthropic-sdk-go/option"
)
func main() {
client := anthropic.NewClient(
option.WithAPIKey("my-anthropic-api-key"),
)
betaMessage, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
MaxTokens: 1024,
Messages: []anthropic.BetaMessageParam{anthropic.BetaMessageParam{
Content: []anthropic.BetaContentBlockParamUnion{anthropic.BetaContentBlockParamUnion{
OfText: &anthropic.BetaTextBlockParam{Text: "What is a quaternion?", CacheControl: anthropic.BetaCacheControlEphemeralParam{TTL: anthropic.BetaCacheControlEphemeralTTLTTL5m}, Citations: []anthropic.BetaTextCitationParamUnion{anthropic.BetaTextCitationParamUnion{
OfCharLocation: &anthropic.BetaCitationCharLocationParam{CitedText: "cited_text", DocumentIndex: 0, DocumentTitle: anthropic.String("x"), EndCharIndex: 0, StartCharIndex: 0},
}}},
}},
Role: anthropic.BetaMessageParamRoleUser,
}},
Model: anthropic.ModelClaude3_7SonnetLatest,
})
if err != nil {
panic(err.Error())
}
fmt.Printf("%+v\n", betaMessage.ID)
}
{
"id": "msg_013Zva2CMHLNnXjNJJKqJ2EF",
"container": {
"id": "id",
"expires_at": "2019-12-27T18:11:19.117Z",
"skills": [
{
"skill_id": "x",
"type": "anthropic",
"version": "x"
}
]
},
"content": [
{
"citations": [
{
"cited_text": "cited_text",
"document_index": 0,
"document_title": "document_title",
"end_char_index": 0,
"file_id": "file_id",
"start_char_index": 0,
"type": "char_location"
}
],
"text": "Hi! My name is Claude.",
"type": "text"
}
],
"context_management": {
"applied_edits": [
{
"cleared_input_tokens": 0,
"cleared_tool_uses": 0,
"type": "clear_tool_uses_20250919"
}
]
},
"model": "claude-sonnet-4-5-20250929",
"role": "assistant",
"stop_reason": "end_turn",
"stop_sequence": null,
"type": "message",
"usage": {
"cache_creation": {
"ephemeral_1h_input_tokens": 0,
"ephemeral_5m_input_tokens": 0
},
"cache_creation_input_tokens": 2051,
"cache_read_input_tokens": 2051,
"input_tokens": 2095,
"output_tokens": 503,
"server_tool_use": {
"web_fetch_requests": 2,
"web_search_requests": 0
},
"service_tier": "standard"
}
}Returns Examples
{
"id": "msg_013Zva2CMHLNnXjNJJKqJ2EF",
"container": {
"id": "id",
"expires_at": "2019-12-27T18:11:19.117Z",
"skills": [
{
"skill_id": "x",
"type": "anthropic",
"version": "x"
}
]
},
"content": [
{
"citations": [
{
"cited_text": "cited_text",
"document_index": 0,
"document_title": "document_title",
"end_char_index": 0,
"file_id": "file_id",
"start_char_index": 0,
"type": "char_location"
}
],
"text": "Hi! My name is Claude.",
"type": "text"
}
],
"context_management": {
"applied_edits": [
{
"cleared_input_tokens": 0,
"cleared_tool_uses": 0,
"type": "clear_tool_uses_20250919"
}
]
},
"model": "claude-sonnet-4-5-20250929",
"role": "assistant",
"stop_reason": "end_turn",
"stop_sequence": null,
"type": "message",
"usage": {
"cache_creation": {
"ephemeral_1h_input_tokens": 0,
"ephemeral_5m_input_tokens": 0
},
"cache_creation_input_tokens": 2051,
"cache_read_input_tokens": 2051,
"input_tokens": 2095,
"output_tokens": 503,
"server_tool_use": {
"web_fetch_requests": 2,
"web_search_requests": 0
},
"service_tier": "standard"
}
}