What are Agent Skills
Agent Skills are a way to package expertise, including instructions, scripts, and reference material, turning them into a folder that Claude can discover and use automatically when it's relevant. They turn a capable generalist into a knowledgeable specialist that follows your procedures.
The core idea
A Skill is a folder with a
SKILL.mdfile (plus optional scripts and resources) that teaches Claude how to do a specific kind of task the way you want it done.
Think of it like an onboarding guide for a new team member: the steps, the standards, the templates, the do's and don'ts, written once, applied every time.
Why Skills beat re-prompting
| Without Skills | With Skills |
|---|---|
| Re-explain the procedure each time | Claude already knows it |
| Inconsistent results across chats/people | Consistent, repeatable output |
| Knowledge lives in one person's head | Knowledge is packaged and shareable |
How Claude uses them (progressive disclosure)
Skills are efficient by design:
- Claude first sees only a Skill's name and description (lightweight metadata).
- If a task looks relevant, it reads the full
SKILL.md. - Only if needed does it open additional bundled files (references, scripts).
This "progressive disclosure" means you can have many Skills available without bloating Claude's context; it loads detail only when required.
Where Skills work
Agent Skills are supported across Claude's surfaces, including claude.ai, Claude Code, the API, and the Agent SDK, and have been published as an open standard for portability across tools. A Skill you write is reusable wherever Skills are supported.
Two kinds of Skills
- Built-in / pre-built: ready-made Skills from Anthropic, e.g. creating PowerPoint, Excel, Word, and PDF files. See Using built-in skills.
- Custom: Skills you create to capture your own workflows and standards. See Creating your own skill.
Skills vs. Projects vs. MCP
These complement each other:
- Projects hold context for a body of work.
- Skills hold procedural know-how Claude applies across tasks.
- MCP connects Claude to external tools and data.
A single task might use all three: a Skill defines how to produce a report, a Project supplies the context, and MCP pulls in the live data.
Next: put ready-made Skills to work with built-in skills.