Agent Skills (by Anthropic)

What it is

A skill is a folder with a SKILL.md: a name, a description and your instructions. Claude only sees the name and description at first (about 100 tokens per skill) and loads the rest when a task needs it. Anthropic's official repo has 19 ready-made ones.

Setup

1. Add Anthropic's skills to Claude Code

   /plugin marketplace add anthropics/skillsCopy

2. Install a set: the documents (PDF, Word, Excel, PowerPoint) or the examples (skill-creator included)

   /plugin install document-skills@anthropic-agent-skillsCopy
   /plugin install example-skills@anthropic-agent-skillsCopy

3. Or write your own: one folder, one file

   ~/.claude/skills/commit-style/SKILL.mdCopy

4. Start that file with a --- block holding a name and a description that says when to use it ("Use when writing a git commit message"), then write your rules below it.

Cheat sheet

• Use it for anything you keep re-explaining: your commit format, your brand voice, your checklists.
• The description decides when it fires. Vague description, no skill.
• Keep SKILL.md short (under 500 lines) and move long references to other files in the folder.
• Skip it for one-off tasks. A skill pays off the second time you'd repeat yourself.
• The PDF, Word, Excel and PowerPoint skills are source-available, not open source. Most of the others are Apache 2.0.

Axo's take

AXO

Taught it my commit format once. Haven't retyped it since.