Claude SDK for Go

The Claude SDK for Go provides access to the Claude API from Go applications.

Documentation

Full documentation is available at platform.claude.com/docs/en/api/sdks/go.

Installation

import (
	"github.com/anthropics/anthropic-sdk-go/v2" // imported as anthropic
)

Or explicitly add the dependency:

go get -u 'github.com/anthropics/anthropic-sdk-go/[email protected]'

Getting started

package main
import (
	"context"
	"fmt"
"github.com/anthropics/anthropic-sdk-go/v2"
	"github.com/anthropics/anthropic-sdk-go/v2/option"
)
func main() {
	client := anthropic.NewClient(
		option.WithAPIKey("my-anthropic-api-key"), // defaults to os.LookupEnv("ANTHROPIC_API_KEY")
	)
	message, err := client.Messages.New(context.TODO(), anthropic.MessageNewParams{
		MaxTokens: 1024,
		Messages: []anthropic.MessageParam{
			anthropic.NewUserMessage(anthropic.NewTextBlock("What is a quaternion?")),
		},
		Model: anthropic.ModelClaudeOpus5_5,
	})
	if err != nil {
		panic(err.Error())
	}
	fmt.Printf("%+v\n", message.Content)
}

OpenTelemetry

The SDK reports each API call as an OpenTelemetry span when your application has registered a tracer provider. No client option is needed for that. The spans carry no content of requests or responses unless you set option.WithOpenTelemetryTracesContentMode(option.OpenTelemetryContentModeContent) or ANTHROPIC_OPEN_TELEMETRY_TRACES_CONTENT_MODE=content. A span then holds at most 750,000 bytes of content, and has anthropic.content.truncated when content was cut or left out to fit; option.WithOpenTelemetryTracesMaxContentBytes(n) or ANTHROPIC_OPEN_TELEMETRY_TRACES_MAX_CONTENT_BYTES=n sets another maximum. Each request carries the trace context of its span in the headers of your registered propagator; option.WithOpenTelemetryPropagation(false) or ANTHROPIC_OPEN_TELEMETRY_PROPAGATION=false leaves them out, for an application whose HTTP client instrumentation already sends them.

client := anthropic.NewClient(option.WithTracerProvider(provider)) // a provider other than the registered one
quiet := anthropic.NewClient(option.WithoutOpenTelemetry())        // no spans; ANTHROPIC_OPEN_TELEMETRY=false does the same
client.Messages.New(ctx, params, option.WithOpenTelemetryConversationID(conversationID)) // sets gen_ai.conversation.id

WithTracerProvider, WithOpenTelemetryPropagation, WithoutOpenTelemetry, WithOpenTelemetryTraces, WithOpenTelemetryTracesContentMode, and WithOpenTelemetryTracesMaxContentBytes are client options. Go has one request option type, so a method call accepts them too; passed that way, they apply to that call only.

Requirements

Go 1.25+

Contributing

See CONTRIBUTING.md.

License

This project is licensed under the Apache License, Version 2.0. See the LICENSE file for details. Versions released before the change from the MIT License, and third-party contributions merged before it, remain under the MIT License. See LICENSE-MIT.