Claude API — Go

Note: The Go SDK supports the Claude API. Tool runner and Agent SDK are not yet available for Go — use the manual agentic loop for tool use.

Installation

```bash go get github.com/anthropics/anthropic-sdk-go ```

Client Initialization

```go import ( "github.com/anthropics/anthropic-sdk-go" "github.com/anthropics/anthropic-sdk-go/option" )

// Default (uses ANTHROPIC_API_KEY env var) client := anthropic.NewClient()

// Explicit API key client := anthropic.NewClient( option.WithAPIKey("your-api-key"), ) ```

Basic Message Request

```go response, err := client.Messages.New(context.TODO(), anthropic.MessageNewParams{ Model: anthropic.ModelClaudeOpus4_6, MaxTokens: 1024, Messages: []anthropic.MessageParam{ anthropic.NewUserMessage(anthropic.NewTextBlock("What is the capital of France?")), }, }) if err != nil { log.Fatal(err) } fmt.Println(response.Content[0].Text) ```

Streaming

```go stream := client.Messages.NewStreaming(context.TODO(), anthropic.MessageNewParams{ Model: anthropic.ModelClaudeOpus4_6, MaxTokens: 1024, Messages: []anthropic.MessageParam{ anthropic.NewUserMessage(anthropic.NewTextBlock("Write a haiku")), }, })

for stream.Next() { event := stream.Current() switch eventVariant := event.AsAny().(type) { case anthropic.ContentBlockDeltaEvent: switch deltaVariant := eventVariant.Delta.AsAny().(type) { case anthropic.TextDelta: fmt.Print(deltaVariant.Text) } } } if err := stream.Err(); err != nil { log.Fatal(err) } ```

Tool Use (Manual Loop)

The Go SDK supports raw tool definitions via JSON schema. See the shared tool use concepts for the tool definition format and agentic loop pattern.

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