Agents, MCP & Skills · 2 min read · Updated 2026-10-09
How Claude Skills work
Step 1: a short label
At the start, Claude knows each skill by its name and one-line description only. That is a few words per skill, so you can have many skills without slowing Claude down.
Step 2: the full instructions
When your request fits a description, Claude reads the whole SKILL.md and follows it. This is why the description matters most: it tells Claude when to use the skill.
Step 3: extra files and scripts
A skill can point to other files, like a template or a style guide, and to scripts that do exact work, such as filling a form. Claude opens or runs these only when needed.
Writing a good skill
Make the description say what the skill does and when to use it. Keep the steps short and clear. Test it on a real task and fix what goes wrong.
Key takeaways
- Claude loads skills in steps, only as needed.
- The description decides when a skill is used.
- Scripts handle exact work that words cannot.
Quick questions
Why not put everything in one long prompt?
A long prompt uses space in every chat. A skill is loaded only when it is relevant.
Can skills run code?
Yes, a skill can include scripts that Claude runs where code execution is available.
What if Claude does not use my skill?
Make the description clearer about when it applies, and test again.