Skills: On-Demand Expertise
A Skill packages expertise — instructions plus optional scripts and resources — that Claude loads only when relevant. Instead of stuffing everything into CLAUDE.md, you give Claude a library of capabilities it pulls in on demand.
Anatomy
A skill is a folder with a SKILL.md: YAML frontmatter + instructions.
---
name: pdf-forms
description: Use when the user needs to fill, read, or generate PDF forms.
---
# PDF Forms
Steps and rules for working with PDF forms…
(optionally reference scripts/ or resources/ in this folder)
The description is the trigger — Claude reads it to decide when to activate the skill. Write it as "Use when…", specific enough that it loads at the right time and not otherwise.
Progressive disclosure (why skills scale)
Claude doesn't load every skill's full body up front — it sees the lightweight name + description, and only pulls in the full instructions (and runs scripts) when a request matches. That keeps context lean even with many skills installed.
Where they live
- Personal:
~/.claude/skills/<name>/SKILL.md - Project (shareable):
.claude/skills/<name>/SKILL.md - Bundled in a plugin for team distribution.
AILmanac ships 7 ready-made skill packs — copy one in to try it.
Skill vs command vs subagent vs MCP
| Tool | What it is | You vs Claude triggers |
|---|---|---|
| Slash command | A saved prompt | You invoke it |
| Skill | On-demand expertise + scripts | Claude loads it when relevant |
| Subagent | A delegated agent with its own context | Claude delegates |
| MCP | A connection to external tools/data | Provides tools to call |