unsupported-frontmatter

To validate YAML frontmatter, you can run a validator against the skill directory to detect unsupported metadata fields. This process checks the SKILL.md file to ensure only supported keys are present, returning a structured exclusion reason if extraneous fields are found.

When skill discovery finds extraneous frontmatter fields, the validator rejects the invalid skill and prevents it from propagating. It emits a clear exclusion reason and provides guidance to fix the metadata before publishing.

No specific dependencies are required to check for unsupported metadata in SKILL.md files. The validator operates as a standalone tool to inspect YAML frontmatter and identify any keys not supported by the ecosystem.

Your skill definition is rejected during adapter integration because it contains unsupported frontmatter fields. The validator requires YAML frontmatter with only a name and description, rejecting extraneous keys to prevent adapter conflicts.

Yes, you can integrate this validator with local validation workflows to block the publishing of invalid skills. It detects unsupported YAML keys in SKILL.md frontmatter and emits guidance to fix metadata before release.