YAML Frontmatter
The metadata block at the top of SKILL.md files that Claude Code parses to discover and describe available skills.
YAML frontmatter is the machine-readable header between --- delimiters at the top of every SKILL.md file. It contains the skill description, trigger phrases, and category information that Claude Code needs to discover and invoke the skill. Without valid YAML frontmatter, a skill is invisible. Two hard rules: never nest double quotes inside double-quoted YAML strings (use single quotes for trigger phrases), and every SKILL.md must start with a --- block containing at minimum a description field. A 2026-02-11 audit found 37 of 52 skills had broken frontmatter. All were fixed, and validation is now part of the weekly repo audit.
Where it shows up:
Related Terms
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Agent Layer
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