# agentskills.io These rules validate skills against the [agentskills.io specification](https://agentskills.io/specification). They auto-enable wherever skills are detected — agentskills repos, single plugins, marketplaces, `.claude/` directories, Codex plugins and marketplaces, Grok Build plugins and marketplaces, and Agent Plugin packages. | Rule ID | Description | Default Severity | Autofix | |---------|-------------|------------------|---------| | [`agentskill-valid`](agentskill-valid.md) | SKILL.md must have valid frontmatter with name and description | error (auto) | auto | | [`agentskill-name`](agentskill-name.md) | Skill name must be lowercase letters, numbers, and hyphens and match directory name | error (auto) | auto | | [`agentskill-rename-refs`](agentskill-rename-refs.md) | Update stale skill name references after a rename | warning (auto) | auto | | [`agentskill-description`](agentskill-description.md) | Skill description should be meaningful and within length limits | warning (auto) | - | | [`agentskill-structure`](agentskill-structure.md) | Skill directories should only contain recognized subdirectories (stricter than spec) | warning (disabled) | - | | [`agentskill-evals`](agentskill-evals.md) | Validate evals/evals.json format when present | warning (auto) | - | | [`agentskill-evals-required`](agentskill-evals-required.md) | Require evals/evals.json for each skill (opt-in) | warning (disabled) | - | | [`agentskill-unreferenced-files`](agentskill-unreferenced-files.md) | Every bundled skill file should be referenced from SKILL.md, directly or transitively | warning (auto) | - |