Anthropic Messages API

The primary interface for building Claude-powered applications via structured, multi-turn message arrays.

Anthropic's Messages API serves as the gateway to Claude 3.5 Sonnet and the Opus model family. It replaces the legacy Text Completions endpoint with a robust, role-based structure (user vs. assistant) that supports multi-modal inputs like images and PDFs. Developers use this API to manage context windows up to 200k tokens, implement tool use (function calling), and stream real-time responses with sub-second time-to-first-token performance.

https://docs.anthropic.com/en/api/messages