Frontmatter
The YAML block between opening and closing --- lines at the top of SKILL.md that carries a skill's metadata.
- Published
- Sep 27, 2026
- Checked
- Sep 27, 2026
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Signed by Ravalika Korthiwada, Sep 27, 2026. Passing one check says nothing about the next.
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Frontmatter is the YAML block between the opening and closing --- lines at the top of SKILL.md. The Agent Skills specification requires two fields inside it: name and description. Optional fields include license, compatibility, metadata and the experimental allowed-tools. A host reads this block first, before any of the skill’s instructions, which is what makes progressive disclosure possible: a skill’s metadata is cheap to hold in context even when its full instructions aren’t loaded yet.
Our explain-error skill’s frontmatter reads:
name: explain-error
description: Explains a pasted error message or stack trace and suggests one concrete fix. Use when someone shares an error, exception, stack trace, or traceback and asks what is wrong or how to fix it.We validated this frontmatter with npx skills-ref validate (skills-ref v0.1.5) on September 27, 2026, which reported it as a valid skill. That check only inspects frontmatter shape (a name matching the folder, a non-empty description); it does not check whether the instructions below are followed correctly or whether files the instructions reference actually exist.
Related: SKILL.md, Agent skill, Skill activation.