Conciseness

The opening paragraph ("Unit tests catch bugs before they reach production, serve as documentation for expected behavior, and give developers confidence to refactor code without breaking functionality") explains motivation Claude already knows, and the "Explain" section ("Explain how unit tests catch bugs early and serve as documentation for expected behavior") restates it almost verbatim. The rest is lean, so this is 'Mostly efficient but includes some unnecessary explanation or could be tightened' — a 2 would require several padded sections, and only one exists.

Actionability

The Quick Reference bullets give concrete heuristics ("Aim for 80%+ coverage on critical paths", "Mock external dependencies, not internal modules"), but the Check/Fix sections are single-sentence directives ("Write unit tests for untested functions and components to improve code reliability") with no commands or examples in the body; all executable specifics are deferred to references/rule.md. As an instruction-only skill this is 'Some concrete guidance but incomplete ... missing key details' rather than the mostly-executable guidance of a 4.

Workflow Clarity

The Check → Fix → Code Review sections imply a progression (find gaps, write tests, review enforcement), but no validation checkpoint exists — nothing like running the new tests or confirming the coverage threshold after "Write unit tests for untested functions". This matches 'Steps listed but validation gaps; sequence present but checkpoints missing or implicit'; a 4 would need most checkpoints present, and the simple-skill exception does not apply because the implied check-then-fix workflow has no verification step.

Progressive Disclosure

The body is a short, well-sectioned overview (Quick Reference, Check, Fix, Explain, Code Review) that delegates all implementation detail via a clearly signaled, one-level-deep pointer: "For full implementation details, code examples, and framework-specific guidance, see `references/rule.md`" — and that file exists in the bundle. This matches 'Clear overview with well-signaled one-level-deep references; content appropriately split; easy navigation'.

Specificity

The description names the domain ("CI coverage, automated checks, or test strategy related to Write unit tests") and one concrete action ("reviewing") plus a review focus ("Focus on whether the rule is continuously verified, not just documented"), but never states the skill's core capability as an explicit action. This matches the anchor 'Names domain and 1-2 concrete actions, but not comprehensive'; a 4 would require several distinct specific actions listed, which is not the case here.

Completeness

The 'when' is explicit and strong ("Use when reviewing CI coverage, automated checks, or test strategy related to Write unit tests"), and a 'what' is present but indirect ("Focus on whether the rule is continuously verified, not just documented") — the core capability only appears embedded in the when-clause. Both are present with one that could be sharper, fitting the anchor 'Has both what and when; when could be more explicit or specific' (here it is the 'what' that could be more explicit), so not a 3 (the when is not missing or weakly implied) nor a 5 (the what is not clearly and explicitly stated as a concrete capability).

Trigger Term Quality

Natural terms a user would say are present: "CI coverage", "automated checks", "test strategy", "unit tests". Common variations like "testing", "test coverage", "TDD", or "regression tests" are missing, matching the anchor 'Good keyword coverage; a few natural terms missing' rather than the comprehensive synonym/file-extension coverage of a 5.

Distinctiveness Conflict Risk

The scope is fairly narrow — reviewing verification/enforcement of the unit-tests rule ("Flag exact gaps where the rule is not automatically verified" territory, implied by "continuously verified, not just documented") — but terms like "automated checks" and "test strategy" carry minor overlap risk with generic testing or CI/CD skills. This fits 'Mostly distinct; minor overlap risk with closely related skills' rather than the clear-niche-with-minimal-conflict of a 5.