Learn what Claude Code Skills are, how they work, and why they're the recommended way to extend Claude Code's capabilities. This lesson covers the essential concepts — where Skills live, how they're structured, and the invocation model that lets Claude discover and use them automatically or lets you trigger them manually with a slash command.
From the folder structure of a Skill to the critical role of the description field in auto-discovery, you'll understand everything you need before building your first custom Skill. You'll also learn how Skills differ from the older custom commands system and why Skills are more powerful and context-efficient.
- What Skills are and why Anthropic is unifying everything under Skills
- The folder structure: SKILL.md plus optional scripts, references, and supporting files
- Personal Skills (~/.claude/skills/) vs Project Skills (.claude/skills/)
- How auto-discovery works through description matching
- Controlling invocation with disable-model-invocation and user-invocable
- How Skills stay context-efficient — content only loads when a Skill is actually invoked
- The relationship between Skills and the older custom commands system