Create a Text Completion

completions.create(**kwargs) -> Completion { id, completion, model, 2 more }

POST/v1/complete

[Legacy] Create a Text Completion.

The Text Completions API is a legacy API. We recommend using the Messages API going forward.

Future models and features will not be compatible with Text Completions. See our migration guide for guidance in migrating from Text Completions to Messages.

ParametersExpand Collapse

max_tokens_to_sample: Integer

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.

minimum1

model: Model

The model that will complete your prompt.

See models for additional details and options.

Accepts one of the following:

:"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.

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

String

prompt: String

The prompt that you want Claude to complete.

For proper response generation you will need to format your prompt using alternating `

Human:and

Assistant:` conversational turns. For example:

"

Human: {userQuestion}

Assistant:"

See prompt validation and our guide to prompt design for more details.

minLength1

metadata: Metadata { user_id }

An object describing metadata about the request.

user_id: String

An external identifier for the user who is associated with the request.

This should be a uuid, hash value, or other opaque identifier. Anthropic may use this id to help detect abuse. Do not include any identifying information such as name, email address, or phone number.

maxLength256

stop_sequences: Array[String]

Sequences that will cause the model to stop generating.

Our models stop on `"

Human:"`, and may include additional built-in stop sequences in the future. By providing the stop_sequences parameter, you may include additional strings that will cause the model to stop generating.

stream: false

Whether to incrementally stream the response using server-sent events.

See streaming for details.

temperature: Float

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.

maximum1

minimum0

top_k: Integer

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.

minimum0

top_p: Float

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.

maximum1

minimum0

anthropic_beta: Array[AnthropicBeta]

Optional header to specify the beta version(s) you want to use.

Accepts one of the following:

String

:"message-batches-2024-09-24" | :"prompt-caching-2024-07-31" | :"computer-use-2024-10-22" | 17 more

Accepts one of the following:

:"message-batches-2024-09-24"

:"prompt-caching-2024-07-31"

:"computer-use-2024-10-22"

:"computer-use-2025-01-24"

:"pdfs-2024-09-25"

:"token-counting-2024-11-01"

:"token-efficient-tools-2025-02-19"

:"output-128k-2025-02-19"

:"files-api-2025-04-14"

:"mcp-client-2025-04-04"

:"mcp-client-2025-11-20"

:"dev-full-thinking-2025-05-14"

:"interleaved-thinking-2025-05-14"

:"code-execution-2025-05-22"

:"extended-cache-ttl-2025-04-11"

:"context-1m-2025-08-07"

:"context-management-2025-06-27"

:"model-context-window-exceeded-2025-08-26"

:"skills-2025-10-02"

:"fast-mode-2026-02-01"

ReturnsExpand Collapse

class Completion { id, completion, model, 2 more }

id: String

Unique object identifier.

The format and length of IDs may change over time.

completion: String

The resulting completion up to and excluding the stop sequences.

model: Model

The model that will complete your prompt.

See models for additional details and options.

Accepts one of the following:

:"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.

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

String

stop_reason: String

The reason that we stopped.

This may be one the following values:

"stop_sequence": we reached a stop sequence — either provided by you via the stop_sequences parameter, or a stop sequence built into the model
"max_tokens": we exceeded max_tokens_to_sample or the model's maximum

type: :completion

Object type.

For Text Completions, this is always "completion".

class Completion { id, completion, model, 2 more }

id: String

Unique object identifier.

The format and length of IDs may change over time.

completion: String

The resulting completion up to and excluding the stop sequences.

model: Model

The model that will complete your prompt.

See models for additional details and options.

Accepts one of the following:

:"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.

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

String

stop_reason: String

The reason that we stopped.

This may be one the following values:

"stop_sequence": we reached a stop sequence — either provided by you via the stop_sequences parameter, or a stop sequence built into the model
"max_tokens": we exceeded max_tokens_to_sample or the model's maximum

type: :completion

Object type.

For Text Completions, this is always "completion".

Create a Text Completion

require "anthropic"

anthropic = Anthropic::Client.new(api_key: "my-anthropic-api-key")

completion = anthropic.completions.create(
  max_tokens_to_sample: 256,
  model: :"claude-opus-4-6",
  prompt: "\n\nHuman: Hello, world!\n\nAssistant:"
)

puts(completion)

Response 200

{
  "id": "compl_018CKm6gsux7P8yMcwZbeCPw",
  "completion": " Hello! My name is Claude.",
  "model": "claude-2.1",
  "stop_reason": "stop_sequence",
  "type": "completion"
}

Returns Examples

Response 200

{
  "id": "compl_018CKm6gsux7P8yMcwZbeCPw",
  "completion": " Hello! My name is Claude.",
  "model": "claude-2.1",
  "stop_reason": "stop_sequence",
  "type": "completion"
}

require "anthropic" anthropic = Anthropic::Client.new(api_key: "my-anthropic-api-key") completion = anthropic.completions.create( max_tokens_to_sample: 256, model: :"claude-opus-4-6", prompt: "\n\nHuman: Hello, world!\n\nAssistant:" ) puts(completion)