@anthropic-ai/sdk

Overview

The official TypeScript library for the Anthropic API. The full API documentation can be found at platform.claude.com/docs or in api.md.

Installation

npm install @anthropic-ai/sdk

Core API / Usage

npm install @anthropic-ai/sdk

import Anthropic from '@anthropic-ai/sdk';

const client = new Anthropic({
  apiKey: process.env['ANTHROPIC_API_KEY'], // This is the default and can be omitted
});

const message = await client.messages.create({
  max_tokens: 1024,
  messages: [{ role: 'user', content: 'Hello, Claude' }],
  model: 'claude-sonnet-4-5-20250929',
});

console.log(message.content);

Common Patterns

Pattern 1

import Anthropic from '@anthropic-ai/sdk';

const client = new Anthropic();

const stream = await client.messages.create({
  max_tokens: 1024,
  messages: [{ role: 'user', content: 'Hello, Claude' }],
  model: 'claude-sonnet-4-5-20250929',
  stream: true,
});
for await (const messageStreamEvent of stream) {
  console.log(messageStreamEvent.type);
}

Pattern 2

import Anthropic from '@anthropic-ai/sdk';

const client = new Anthropic({
  apiKey: process.env['ANTHROPIC_API_KEY'], // This is the default and can be omitted
});

const params: Anthropic.MessageCreateParams = {
  max_tokens: 1024,
  messages: [{ role: 'user', content: 'Hello, Claude' }],
  model: 'claude-sonnet-4-5-20250929',
};
const message: Anthropic.Message = await client.messages.create(params);

Pattern 3

const message = await client.messages.create(...)
console.log(message.usage)
// { input_tokens: 25, output_tokens: 13 }

Configuration

import Anthropic from '@anthropic-ai/sdk';

const client = new Anthropic({
  apiKey: process.env['ANTHROPIC_API_KEY'], // This is the default and can be omitted
});

const message = await client.messages.create({
  max_tokens: 1024,
  messages: [{ role: 'user', content: 'Hello, Claude' }],
  model: 'claude-sonnet-4-5-20250929',
});

console.log(message.content);

Tips & Gotchas

• Includes built-in TypeScript type definitions.
• Current version: 0.78.0. Check the changelog when upgrading across major versions.