What are Claude skills?

A skill is a folder of instructions — at minimum a single SKILL.md file — that teaches Claude how to do a specific job well: a format it should write correctly, a workflow it should follow, a tool it should drive. Installed skills load automatically when your request matches what they cover.

The shape of one

A markdown file with a name and a description in its frontmatter, instructions in its body, and optionally a references/ folder for deep material and scripts/ for code the agent can run. They range from 41 lines (defuddle, which cleans web pages into markdown) to full production kits (video-shotcraft's current test ships 51.1MB of shot recipes, templates, and media). The format is an open spec, so the same skill works in Claude Code, Codex, Cursor and others.

Skills vs plugins, commands, MCP

Slash commands are entry points you type; MCP servers give the model live tools and data; plugins bundle any of the above for distribution. Skills are the knowledge layer — the model reads them and applies judgment. The lines blur in practice: big systems like GSD Core install commands, agents, hooks and skills in one shot.

Getting one

npx skills add owner/repo -a claude-code -y

Two to three seconds later it lives in .claude/skills/. Which ones are worth those seconds is this site's entire subject: we install and run them so you can pick from measured results rather than star counts — starting with eight practices we learned the empirical way.