Code documentation standards

Write effective code documentation. Levels: 1. Code comments (explain why, not what - complex logic only). 2. Function/method docs (parameters, return values, exceptions - JSDoc, docstrings). 3. README (setup, usage, examples). 4. API documentation (OpenAPI/Swagger for REST). 5. Architecture docs (system design, diagrams). 6. Changelog (version history). Best practices: Keep docs close to code. Update with code changes. Use examples. Avoid obvious comments. Document assumptions and edge cases. Use diagrams (C4 model, UML). Tools: Sphinx, Doxygen, MkDocs. Good code is self-documenting, but docs add context.