API Lab MCP is an MCP server that lets you test, debug, and document APIs through natural conversation with Claude. It integrates directly with Claude Desktop and Claude Code, enabling you to test APIs by describing what you want rather than writing scripts. The server supports universal authentication methods (Bearer tokens, API keys, OAuth2, session cookies, and CSRF tokens) to secure test sessions. It provides intelligent response analysis with automatic validation of status codes, headers, and JSON paths, and it reports real-time performance metrics such as response times, payload sizes, and Core Web Vitals. The tooling supports conversational testing to model complex scenarios, spec-based test generation from OpenAPI/Swagger docs, and batch testing to run multiple APIs in parallel or in sequence. It also enables MCP server testing to assess other MCP tools and resources, and environment management to switch between development, staging, and production. With auto-documentation from test conversations and straightforward installation options for Claude Code, Claude Desktop, and Docker, API Lab MCP aims to reduce context switching and accelerate API testing workflows.