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.

Parameters

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.

Betas param.Field[[]AnthropicBeta] Optional

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

string

type AnthropicBeta string

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"

const AnthropicBetaFastMode2026_02_01 AnthropicBeta = "fast-mode-2026-02-01"

const AnthropicBetaOutput300k2026_03_24 AnthropicBeta = "output-300k-2026-03-24"

const AnthropicBetaUserProfiles2026_03_24 AnthropicBeta = "user-profiles-2026-03-24"

const AnthropicBetaUserProfiles2026_08_18 AnthropicBeta = "user-profiles-2026-08-18"

const AnthropicBetaAdvisorTool2026_03_01 AnthropicBeta = "advisor-tool-2026-03-01"

const AnthropicBetaManagedAgents2026_04_01 AnthropicBeta = "managed-agents-2026-04-01"

const AnthropicBetaCacheDiagnosis2026_04_07 AnthropicBeta = "cache-diagnosis-2026-04-07"

const AnthropicBetaDreaming2026_04_21 AnthropicBeta = "dreaming-2026-04-21"

const AnthropicBetaThinkingTokenCount2026_05_13 AnthropicBeta = "thinking-token-count-2026-05-13"

const AnthropicBetaServerSideFallback2026_06_01 AnthropicBeta = "server-side-fallback-2026-06-01"

const AnthropicBetaServerSideFallback2026_07_01 AnthropicBeta = "server-side-fallback-2026-07-01"

const AnthropicBetaFallbackCredit2026_06_01 AnthropicBeta = "fallback-credit-2026-06-01"

const AnthropicBetaFallbackCredit2026_07_01 AnthropicBeta = "fallback-credit-2026-07-01"

const AnthropicBetaAgentMemory2026_07_22 AnthropicBeta = "agent-memory-2026-07-22"

const AnthropicBetaMidConversationToolChanges2026_07_01 AnthropicBeta = "mid-conversation-tool-changes-2026-07-01"

const AnthropicBetaCompact2026_01_12 AnthropicBeta = "compact-2026-01-12"

const AnthropicBetaComputerUse2025_11_24 AnthropicBeta = "computer-use-2025-11-24"

const AnthropicBetaMCPTunnels2026_06_22 AnthropicBeta = "mcp-tunnels-2026-06-22"

const AnthropicBetaStructuredOutputs2025_11_13 AnthropicBeta = "structured-outputs-2025-11-13"

const AnthropicBetaTaskBudgets2026_03_13 AnthropicBeta = "task-budgets-2026-03-13"

const AnthropicBetaThinkingDisplayUpdates2026_08_18 AnthropicBeta = "thinking-display-updates-2026-08-18"

const AnthropicBetaCEUserManagement2026_07_13 AnthropicBeta = "ce-user-management-2026-07-13"

Temperature param.Field[float64] Optional⁠Deprecated

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 of 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

TopK param.Field[int64] Optional⁠Deprecated

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

TopP param.Field[float64] Optional⁠Deprecated

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

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.

One of the following:

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".

defaultcompletion

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.

One of the following:

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".

defaultcompletion

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.ModelClaudeSonnet5,
		Prompt:            "\n\nHuman: Hello, world!\n\nAssistant:",
	})
	if err != nil {
		panic(err.Error())
	}
	fmt.Printf("%+v\n", completion.ID)
}

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

Returns Examples

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