The Claude API offers powerful capabilities beyond basic chat. Tool calling enables function execution with structured schemas - define tools with name, description, and input_schema, then Claude decides when to call them and provides structured arguments. Computer use (beta) allows Claude to control browsers and applications by taking screenshots and executing actions - powerful for web automation and testing. Vision capabilities handle document analysis, chart interpretation, UI screenshots, and multimodal reasoning. Enterprise patterns: implement retry logic with exponential backoff, use streaming for long responses (response.stream()), set system prompts to define Claude role and constraints, implement output caching for repeated similar prompts. Cost optimization: use claude-3-haiku for classification and routing tasks, claude-3-5-sonnet for complex reasoning, batch API for non-real-time processing at 50% cost reduction.