API Fundamentals

Learn how requests flow through base URL, auth headers, and the Messages API.

Send your first POST /v1/messages request with model, max_tokens, and a prompt.

Configure the x-api-key header and environment variables for secure authentication.

Install the anthropic package and initialize a client for your first call.

Reference table for model, max_tokens, temperature, top_p, and top_k parameters.

Compare pricing, capability, and speed tradeoffs across the current Claude model lineup.

Twenty-five practices for reliable authentication, requests, and error handling.