Reference guide to Anthropic's developer API platform for building with Claude programmatically: the Messages API, choosing a model tier (Fable/Opus/Sonnet/Haiku), the agent loop, custom tool use vs. built-in server tools (web search, code execution, web fetch) vs. client tools, extended thinking, S
Reference guide to Anthropic's developer API platform for building with Claude programmatically: the Messages API, choosing a model tier (Fable/Opus/Sonnet/Haiku), the agent loop, custom tool use vs. built-in server tools (web search, code execution, web fetch) vs. client tools, extended thinking, Skills vs. MCP vs. tools, context management patterns (just-in-time context, server-side compaction,