SKM-D01 · Error
`description` is missing
`description` is the other required field, and the sole basis an agent uses to decide whether to load the skill.
What the rule is
`description` is the other required field, and it carries more weight than any other part of the format: at discovery time, a runtime loads only every installed skill's `name` and `description` — not the body, not the bundled files. The description is the entire basis on which an agent decides whether a skill is relevant.
A skill with no description has nothing for that discovery step to match against, in any runtime that implements the standard's progressive-disclosure model.
Where it comes from
- Agent Skills — SpecificationSpecification
- SKILL.md, the format hubSpecification
Which runtimes enforce it
| Runtime | Effect | Note |
|---|---|---|
| Claude Code | Breaks the skill | At discovery time the description is the only thing a runtime sees for a skill — without it there's nothing to trigger on. |
| Codex | Breaks the skill | At discovery time the description is the only thing a runtime sees for a skill — without it there's nothing to trigger on. |
| Cursor | Breaks the skill | At discovery time the description is the only thing a runtime sees for a skill — without it there's nothing to trigger on. |
| OpenClaw | Breaks the skill | At discovery time the description is the only thing a runtime sees for a skill — without it there's nothing to trigger on. |
| Hermes Agent | Breaks the skill | At discovery time the description is the only thing a runtime sees for a skill — without it there's nothing to trigger on. |
How to fix it
- Add a `description` field stating what the skill does and, more importantly, when to use it — written as a trigger condition, not a summary.
Elsewhere
- SKILL.md, the formatThe full frontmatter field table this rule is drawn from.
- Agent Skills Not WorkingThe diagnostic reference this rule’s portability and failure evidence comes from.
- All rulesEvery check the validator runs, grouped by class.