Design system documentation is comprehensive written and visual guidance on how to use design system components, tokens, patterns, and best practices. It explains not just what exists (component inventory), but why it exists and how to use it correctly. Good documentation includes: component usage guidelines (when to use, when not to), design specs (sizes, colors, spacing), code examples (for developers), accessibility requirements, and brand guidelines. It's organized, searchable, and linked from both design tools (Figma) and development environments (Storybook, code comments).