Building a Claude Skill
A Claude Skill is a folder of instructions (and optionally files) that teaches Claude how to do a specific job the way you want it done. Claude reads a short description of every installed skill and loads the right one automatically when your request matches — no menu, no re-pasting.
Why skills are different
A Custom GPT is a destination — you open it, use it, leave. A skill is ambient: it sits in the background across your normal Claude conversations, and Claude reaches for it on its own when the moment fits. Build a skill for turning meeting notes into a client recap, and you just paste your notes into a normal chat and say "make me a recap." Claude notices the match, loads your skill, and follows your exact process. The trigger is automatic. Skills are also portable across Claude's apps and can be bundled and shared with a team.
The mental model
Every skill is a folder with one file: SKILL.md, which has two parts.
- Frontmatter — a few lines at the top between --- markers. The two that matter: name and description. The description is the trigger — Claude reads only the name and description up front and uses the description to decide whether a request is a match.
- Body — plain markdown below the frontmatter: the role, process, rules, output format. Claude reads the full body only once the skill is triggered.
The flow: you make a request → Claude scans skill descriptions → finds a match → loads that skill's full instructions → does the job your way.