Create a Text Completion

client.Completions.New(ctx, params) (*Completion, error)

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

params CompletionNewParams

MaxTokensToSample param.Field[int64]

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 param.Field[Model]

Body param: The model that will complete your prompt.

See models for additional details and options.

Prompt param.Field[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 param.Field[Metadata]optional

Body param: An object describing metadata about the request.

StopSequences param.Field[[]string]optional

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.

Temperature param.Field[float64]optional

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.

maximum1

minimum0

TopK param.Field[int64]optional

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.

minimum0

TopP param.Field[float64]optional

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.

maximum1

minimum0

Betas param.Field[[]AnthropicBeta]optional

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

string

type AnthropicBeta string

Accepts one of the following:

const AnthropicBetaMessageBatches2024_09_24 AnthropicBeta = "message-batches-2024-09-24"

const AnthropicBetaPromptCaching2024_07_31 AnthropicBeta = "prompt-caching-2024-07-31"

const AnthropicBetaComputerUse2024_10_22 AnthropicBeta = "computer-use-2024-10-22"

const AnthropicBetaComputerUse2025_01_24 AnthropicBeta = "computer-use-2025-01-24"

const AnthropicBetaPDFs2024_09_25 AnthropicBeta = "pdfs-2024-09-25"

const AnthropicBetaTokenCounting2024_11_01 AnthropicBeta = "token-counting-2024-11-01"

const AnthropicBetaTokenEfficientTools2025_02_19 AnthropicBeta = "token-efficient-tools-2025-02-19"

const AnthropicBetaOutput128k2025_02_19 AnthropicBeta = "output-128k-2025-02-19"

const AnthropicBetaFilesAPI2025_04_14 AnthropicBeta = "files-api-2025-04-14"

const AnthropicBetaMCPClient2025_04_04 AnthropicBeta = "mcp-client-2025-04-04"

const AnthropicBetaMCPClient2025_11_20 AnthropicBeta = "mcp-client-2025-11-20"

const AnthropicBetaDevFullThinking2025_05_14 AnthropicBeta = "dev-full-thinking-2025-05-14"

const AnthropicBetaInterleavedThinking2025_05_14 AnthropicBeta = "interleaved-thinking-2025-05-14"

const AnthropicBetaCodeExecution2025_05_22 AnthropicBeta = "code-execution-2025-05-22"

const AnthropicBetaExtendedCacheTTL2025_04_11 AnthropicBeta = "extended-cache-ttl-2025-04-11"

const AnthropicBetaContext1m2025_08_07 AnthropicBeta = "context-1m-2025-08-07"

const AnthropicBetaContextManagement2025_06_27 AnthropicBeta = "context-management-2025-06-27"

const AnthropicBetaModelContextWindowExceeded2025_08_26 AnthropicBeta = "model-context-window-exceeded-2025-08-26"

const AnthropicBetaSkills2025_10_02 AnthropicBeta = "skills-2025-10-02"

ReturnsExpand Collapse

type Completion struct{…}

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:

type Model string

The model that will complete your prompt.

See models for additional details and options.

Accepts one of the following:

const ModelClaudeOpus4_5_20251101 Model = "claude-opus-4-5-20251101"

Premium model combining maximum intelligence with practical performance

const ModelClaudeOpus4_5 Model = "claude-opus-4-5"

Premium model combining maximum intelligence with practical performance

const ModelClaude3_7SonnetLatest Model = "claude-3-7-sonnet-latest"

High-performance model with early extended thinking

const ModelClaude3_7Sonnet20250219 Model = "claude-3-7-sonnet-20250219"

High-performance model with early extended thinking

const ModelClaude3_5HaikuLatest Model = "claude-3-5-haiku-latest"

Fastest and most compact model for near-instant responsiveness

const ModelClaude3_5Haiku20241022 Model = "claude-3-5-haiku-20241022"

Our fastest model

const ModelClaudeHaiku4_5 Model = "claude-haiku-4-5"

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

const ModelClaudeHaiku4_5_20251001 Model = "claude-haiku-4-5-20251001"

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

const ModelClaudeSonnet4_20250514 Model = "claude-sonnet-4-20250514"

High-performance model with extended thinking

const ModelClaudeSonnet4_0 Model = "claude-sonnet-4-0"

High-performance model with extended thinking

const ModelClaude4Sonnet20250514 Model = "claude-4-sonnet-20250514"

High-performance model with extended thinking

const ModelClaudeSonnet4_5 Model = "claude-sonnet-4-5"

Our best model for real-world agents and coding

const ModelClaudeSonnet4_5_20250929 Model = "claude-sonnet-4-5-20250929"

Our best model for real-world agents and coding

const ModelClaudeOpus4_0 Model = "claude-opus-4-0"

Our most capable model

const ModelClaudeOpus4_20250514 Model = "claude-opus-4-20250514"

Our most capable model

const ModelClaude4Opus20250514 Model = "claude-4-opus-20250514"

Our most capable model

const ModelClaudeOpus4_1_20250805 Model = "claude-opus-4-1-20250805"

Our most capable model

const ModelClaude3OpusLatest Model = "claude-3-opus-latest"

Excels at writing and complex tasks

const ModelClaude_3_Opus_20240229 Model = "claude-3-opus-20240229"

Excels at writing and complex tasks

const ModelClaude_3_Haiku_20240307 Model = "claude-3-haiku-20240307"

Our previous most fast and cost-effective

string

StopReason 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".

Accepts one of the following:

const CompletionCompletion Completion = "completion"

Create a Text Completion

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"),
  )
  completion, err := client.Completions.New(context.TODO(), anthropic.CompletionNewParams{
    MaxTokensToSample: 256,
    Model: anthropic.ModelClaudeOpus4_5_20251101,
    Prompt: "\n\nHuman: Hello, world!\n\nAssistant:",
  })
  if err != nil {
    panic(err.Error())
  }
  fmt.Printf("%+v\n", completion.ID)
}

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"
}

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"), ) completion, err := client.Completions.New(context.TODO(), anthropic.CompletionNewParams{ MaxTokensToSample: 256, Model: anthropic.ModelClaudeOpus4_5_20251101, Prompt: "\n\nHuman: Hello, world!\n\nAssistant:", }) if err != nil { panic(err.Error()) } fmt.Printf("%+v\n", completion.ID) }