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 / reference validator
- SKILL.md, the format hubSpecification / reference validator
- Agent Skills — Adding skills support to your agent (client-implementation guide)Specification / reference validator
- skills-ref validate (official reference validator, v0.1.5)Specification / reference validator
Strict spec conformance
Non-conformant. The official reference validator (skills-ref) rejects this — tested directly, not inferred from severity.
This is a separate question from the severity above and from which runtimes enforce it below — a rule can be a real, working extension in its home runtime while the reference validator still rejects the file outright, or vice versa. Both facts are reported, never one inferred from the other.
Which runtimes enforce it
| Runtime | Effect | Note |
|---|---|---|
| Claude Code | Not documented | The client-implementation guide's own recommendation is to skip a skill with no description (consistent with a load failure), and skills-ref hard-fails this case — but neither is a citation naming Claude Code, Codex, Cursor, OpenClaw, or Hermes specifically, so no runtime claims a confirmed effect here. |
| Codex | Not documented | The client-implementation guide's own recommendation is to skip a skill with no description (consistent with a load failure), and skills-ref hard-fails this case — but neither is a citation naming Claude Code, Codex, Cursor, OpenClaw, or Hermes specifically, so no runtime claims a confirmed effect here. |
| Cursor | Not documented | The client-implementation guide's own recommendation is to skip a skill with no description (consistent with a load failure), and skills-ref hard-fails this case — but neither is a citation naming Claude Code, Codex, Cursor, OpenClaw, or Hermes specifically, so no runtime claims a confirmed effect here. |
| OpenClaw | Not documented | The client-implementation guide's own recommendation is to skip a skill with no description (consistent with a load failure), and skills-ref hard-fails this case — but neither is a citation naming Claude Code, Codex, Cursor, OpenClaw, or Hermes specifically, so no runtime claims a confirmed effect here. |
| Hermes Agent | Not documented | The client-implementation guide's own recommendation is to skip a skill with no description (consistent with a load failure), and skills-ref hard-fails this case — but neither is a citation naming Claude Code, Codex, Cursor, OpenClaw, or Hermes specifically, so no runtime claims a confirmed effect here. |
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.