Create a Text Completion

$ ant completions create

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.

Parameters

--max-tokens-to-sample: number

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.

minimum1

--model: "claude-fable-5-1" or "claude-mythos-5-1" or "claude-sonnet-5" or 14 more or string

Body param: The model that will complete your prompt.

See models for additional details and options.

--prompt: string

Body param: 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: optional object{ user_id }

Body param: An object describing metadata about the request.

--stop-sequence: optional array of string

Body param: 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.

--beta: optional array of AnthropicBeta

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

--workspace-id: optional string

Header param: Optional header to select the Workspace for this request. The value is a Workspace ID (for example, wrkspc_011CZkZaBF1tNoB5wlCeusgy).

Only needed for credentials that can act on more than one Workspace. A credential that belongs to a specific Workspace may omit it; if sent, it must match that Workspace.

--temperature: optional number⁠Deprecated

Body param: Amount of randomness injected into the response.

Deprecated. Models released after Claude Opus 4.6 do not support setting temperature. A value of 1.0 will be accepted for backwards compatibility, all other values will be rejected with a 400 error.

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: optional number⁠Deprecated

Body param: Only sample from the top K options for each subsequent token.

Deprecated. Models released after Claude Opus 4.6 do not accept top_k; any value will be rejected with a 400 error.

Used to remove "long tail" low probability responses. Learn more technical details here.

Recommended for advanced use cases only.

minimum0

--top-p: optional number⁠Deprecated

Body param: Use nucleus sampling.

Deprecated. Models released after Claude Opus 4.6 do not support setting top_p. A value >= 0.99 will be accepted for backwards compatibility, all other values will be rejected with a 400 error.

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.

Recommended for advanced use cases only.

maximum1

minimum0

Returns

completion: object{ type: "completion", id, completion, 2 more }

type: "completion"

Object type.

For Text Completions, this is always "completion".

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: "claude-fable-5-1" or "claude-mythos-5-1" or "claude-sonnet-5" or 14 more or string

The model that will complete your prompt.

See models for additional details and options.

One of the following:

"claude-fable-5-1"

Frontier intelligence for ambitious tasks across coding, scientific discovery, and enterprise workflows

"claude-mythos-5-1"

Our most capable model for cybersecurity and biology research, available through trusted access programs

"claude-sonnet-5"

High-performance model for coding and agents

"claude-fable-5"

Next generation of intelligence for the hardest knowledge work and coding problems

"claude-mythos-5"

Most capable model for cybersecurity and biology research

"claude-opus-5"

Powerful intelligence for long-running agents and coding

"claude-opus-4-8"

Powerful intelligence for long-running agents and coding

"claude-opus-4-7"

Powerful intelligence for long-running agents and coding

"claude-mythos-preview"

New class of intelligence, strongest in coding and cybersecurity

"claude-opus-4-6"

Powerful intelligence for long-running agents and coding

"claude-sonnet-4-6"

Best combination of speed and intelligence

"claude-haiku-4-5"

Fastest model with near-frontier intelligence

"claude-haiku-4-5-20251001"

Fastest model with near-frontier intelligence

"claude-opus-4-5"

Powerful intelligence for long-running agents and coding

"claude-opus-4-5-20251101"

Powerful intelligence for long-running agents and coding

"claude-sonnet-4-5"

High-performance model for agents and coding

"claude-sonnet-4-5-20250929"

High-performance model for agents and coding

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

Create a Text Completion

ant completions create \
  --api-key my-anthropic-api-key \
  --max-tokens-to-sample 256 \
  --model claude-fable-5-1 \
  --prompt '

Human: Hello, world!

Assistant:'

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"
}