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Sangmin Lee
Sangmin Lee

Posted on • Originally published at claudeguide.io

Claude API Node.js TypeScript Tutorial: Complete Setup Guide (2026)

#claude #node #typescript #anthropic

Originally published at claudeguide.io/claude-api-nodejs-typescript

Claude API Node.js TypeScript Tutorial: Complete Setup Guide (2026)

To use the Claude API with Node.js and TypeScript, install @anthropic-ai/sdk, set ANTHROPIC_API_KEY, and you can send your first typed message in under 15 lines of code. This tutorial walks through installation, authentication, typed request/response patterns, streaming, tool use, prompt caching, and error handling — all with TypeScript examples tested against the current API.

Installation and Project Setup 

npm install @anthropic-ai/sdk
npm install --save-dev typescript @types/node ts-node
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Initialize TypeScript if you haven't already:

npx tsc --init
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Recommended tsconfig.json settings for Claude API projects:

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "strict": true,
    "outDir": "./dist",
    "esModuleInterop": true
  }
}
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Set your API key as an environment variable:

export ANTHROPIC_API_KEY="sk-ant-..."
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Or use a .env file with dotenv:

npm install dotenv
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import 'dotenv/config';
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Your First Typed API Call 

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

const client = new Anthropic();

async function main() {
  const message = await client.messages.create({
    model: 'claude-sonnet-4-5',
    max_tokens: 1024,
    messages: [
      { role: 'user', content: 'Explain TypeScript generics in one paragraph.' }
    ]
  });

  // TypeScript knows this is a TextBlock
  const textBlock = message.content[0];
  if (textBlock.type === 'text') {
    console.log(textBlock.text);
  }
}

main();
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The SDK ships with complete TypeScript types — message.content is typed as `Array<TextBlock | ToolUseBlock

Tool Use (Function Calling) with TypeScript

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

const client = new Anthropic();

// Define a typed tool
const weatherTool: Anthropic.Tool = {
name: 'get_weather',
description: 'Get current weather for a city',
input_schema: {
type: 'object',
properties: {
city: { type: 'string', description: 'City name' },
unit: { type: 'string', enum: ['celsius', 'fahrenheit'] }
},
required: ['city']
}
};

interface WeatherInput {
city: string;
unit?: 'celsius' | 'fahrenheit';
}

async function runWithTools() {
const response = await client.messages.create({
model: 'claude-sonnet-4-5',
max_tokens: 1024,
tools: [weatherTool],
messages: [{ role: 'user', content: "What's the weather in Seoul?" }]
});

if (response.stop_reason === 'tool_use') {
const toolUse = response.content.find(
(b): b is Anthropic.ToolUseBlock =

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