The Claude API is Anthropic's developer interface for accessing Claude's powerful AI capabilities — including natural language understanding, code generation, document analysis, long-context reasoning, and computer use — in any application or workflow. It offers multiple Claude model tiers from fast, affordable Haiku to the highly capable Claude Opus, with a generous 200K token context window that handles entire books, codebases, or document repositories in a single call. Companies building AI-powered products choose the Claude API for its exceptional instruction-following, nuanced reasoning, and Anthropic's Constitutional AI approach to safety.