Install & First Query

# Check if Node.js is installed and what version
node --version
# You need v18.0.0 or higher
# If you see "command not found" or a version below 18,
# install from https://nodejs.org (use the LTS version)

# Add to your shell profile (~/.zshrc or ~/.bashrc)
export ANTHROPIC_API_KEY="sk-ant-api03-your-key-here"

# Reload your shell
source ~/.zshrc

# Create a new directory for your agent project
mkdir my-first-agent && cd my-first-agent

# Initialize a new Node.js project
npm init -y

# Install the Claude Agent SDK
npm install @anthropic-ai/claude-agent

# If you are using TypeScript (recommended):
npm install typescript tsx --save-dev

import { Claude } from "@anthropic-ai/claude-agent";

// Create an agent instance
// It reads ANTHROPIC_API_KEY from your environment automatically
const agent = new Claude({
  model: "claude-sonnet-4-6",  // the model powering your agent
});

// Send a simple query — no tools needed for this one
const result = await agent.query(
  "What are the three most important things to know about building AI agents?"
);

// The result object contains the response text and metadata
console.log(result.text);
// Claude responds with a thoughtful answer about agent architecture

# Run with tsx (TypeScript executor)
npx tsx first-agent.ts

import { Claude } from "@anthropic-ai/claude-agent";

const agent = new Claude({
  model: "claude-sonnet-4-6",
  tools: "defaults",  // enables Bash, Read, Write, Edit, Grep, Glob
});

// Now Claude can actually read your file system
const result = await agent.query(
  "Read the package.json in this directory and list all dependencies."
);

console.log(result.text);
// Claude uses the Read tool to open package.json,
// parses the JSON, and gives you a clean summary

const result = await agent.query("What files are in this directory?");

// The text response from Claude
console.log(result.text);

// How much it cost (in USD)
console.log(result.cost);         // e.g., 0.0042

// How many tool calls were made
console.log(result.toolCalls);    // e.g., 2

// The session ID (for resuming later)
console.log(result.sessionId);   // e.g., "sess_abc123"