If you're building skills for Claude, this is your implementation guide. It walks through the three-level loading system (metadata, SKILL.md body, bundled resources), explains when to use scripts versus reference docs versus assets, and hammers home the core principle: be concise because context window is shared space. The progressive disclosure patterns are especially useful, showing you exactly how to keep SKILL.md under 500 lines by splitting variants and detailed specs into separate files. Think of it as the spec for the spec. Most valuable when you're past your first skill and wondering why Claude isn't picking up your carefully written instructions.
npx skills add https://github.com/composiohq/skills --skill skill-creator