Track 4 · API & Agents
Build Your First Claude API App in 5 Steps
Your first project. 20 minutes.
The OpenAI API gives you direct access to Claude models. This guide walks you through authentication, your first message, streaming, tool use, and the patterns you need to build reliable production systems.
Core Concepts
How the Claude API works
Stateless request/response. You send the full conversation history each time. Claude returns a message object with usage statistics.
Server-sent events deliver tokens as they are generated. Critical for chat interfaces and long-running responses.
Define tools with JSON Schema. Claude calls them intelligently, you execute them, and the results feed back into the conversation.
Set Claude's persona, constraints, and context via the system parameter. Cached system prompts reduce latency and cost.
Tutorial
Getting started step by step
Sign up at console.anthropic.com. Free tier includes enough credits to experiment. Production usage is pay-per-token.
The Anthropic SDK is available for Python and TypeScript/JavaScript. Both are officially maintained.
npm install @anthropic-ai/sdk
# or
pip install anthropicSend a message to Claude claude-sonnet-4-5 and get a response. The API is stateless — you manage conversation history.
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const msg = await client.messages.create({
model: "claude-sonnet-4-5",
max_tokens: 1024,
messages: [{ role: "user", content: "Hello, Claude" }],
});
console.log(msg.content);For real-time UI responses, use the streaming API. Tokens arrive as they are generated — no waiting for the full response.
const stream = await client.messages.stream({
model: "claude-sonnet-4-5",
max_tokens: 1024,
messages: [{ role: "user", content: "Tell me a story" }],
});
for await (const chunk of stream) {
process.stdout.write(chunk.delta?.text ?? "");
}Give Claude tools like web search, database access, or custom functions. Claude decides when to call them and parses the results.
const response = await client.messages.create({
model: "claude-sonnet-4-5",
tools: [{
name: "get_weather",
description: "Get current weather",
input_schema: {
type: "object",
properties: { location: { type: "string" } },
required: ["location"],
},
}],
messages: [{ role: "user", content: "Weather in San Diego?" }],
});Go deeper in the API & Agents track
Track 4 covers the full production surface: error handling, retry logic, rate limiting, prompt caching, multi-agent orchestration, and evaluation. Interactive exercises with a live Claude sandbox so you practice every pattern hands-on.
Ready to build with the Claude API?
Free foundation tracks. Masterclass for advanced patterns.