SKM-P01 · Portability
`paths` is a Cursor-only field
`paths` scopes a skill to files matching glob patterns — it works only in Cursor, and it doesn't just get ignored elsewhere.
What the rule is
`paths` scopes a skill to files matching glob patterns, and it's a Cursor-only frontmatter field — triggering on files touched rather than on phrasing, which is unique to Cursor among the five runtimes this site has verified.
The trap: per a verified, open GitHub issue, adding `paths` to a skill running in Claude Code makes it completely undiscoverable — absent from `/` autocomplete, unlisted, and returning 'Unknown skill' on direct invocation. Removing the single line restores it. What Codex, OpenClaw, and Hermes Agent do with an unrecognised `paths` field isn't documented anywhere we've found — an unrecognised field being silently dropped is common, but not something to assume without evidence (an unrecognised field can just as easily fail validation outright, which is exactly what the official reference validator does with `paths`, having no concept of runtime-specific extensions at all).
Where it comes from
- Cursor — official skills documentationRuntime documentation
- anthropics/claude-code #49835 — `paths` makes a skill undiscoverableVerified issue — open since April 2026
- Agent Skills compatibilityAgentSkills.site
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 | Breaks the skill | Makes the skill entirely undiscoverable: absent from `/` autocomplete, unlisted, and returns 'Unknown skill' on direct invocation. |
| Codex | Not documented | Not documented for this runtime — we hold no runtime-specific evidence either way. |
| Cursor | Enforced (home runtime) | The field's home runtime — scopes triggering to files matching the given glob patterns. |
| OpenClaw | Not documented | Not documented for this runtime — we hold no runtime-specific evidence either way. |
| Hermes Agent | Not documented | Not documented for this runtime — we hold no runtime-specific evidence either way. |
How to fix it
- If the skill needs to run in Claude Code (or any runtime other than Cursor), remove `paths` entirely.
- If file-scoped triggering is genuinely needed, keep this as a Cursor-specific variant of the skill rather than sharing one file across runtimes.
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.