Conciseness

The Philosophy section spends roughly three paragraphs explaining good-vs-bad testing concepts Claude already knows (implementation coupling, tests surviving refactors, mocking internals) before reaching the skill-specific opinion. The rest of the body is lean and directive. Matches anchor 3 ('mostly efficient but includes some unnecessary explanation') rather than 4 because the padding is confined to a whole section, and rather than 2 because only that one section over-explains.

Actionability

Concrete, instruction-level guidance throughout: planning checklists with user-approval gates, an exact question to ask ('What should the public interface look like?'), explicit RED→GREEN cycle rules, a per-cycle checklist, and a concrete pointer to run the /codebase-design skill. Minor gaps keep it below anchor 5 — no test-framework or command specifics and the RED→GREEN blocks are schematic rather than executable. Anchor 4 ('mostly executable guidance... minor gaps') fits; this is acceptable for an instruction-only skill per the scoring notes.

Workflow Clarity

Clear four-phase sequence (Planning → Tracer Bullet → Incremental Loop → Refactor) with explicit checkpoints: each test must fail then pass, 'Never refactor while RED', and 'Run tests after each refactor step', plus checklists. Not anchor 5 because there is no error-recovery/feedback-loop guidance (e.g. what to do when the new test never goes RED, or when minimal code doesn't reach GREEN); stronger than anchor 3 because validation states are explicit rather than implicit.

Progressive Disclosure

The body links to [tests.md](tests.md), [mocking.md](mocking.md), and [refactoring.md](refactoring.md), but none of these files exist in the bundle — there is no references/, scripts/, or assets/ directory. Scored against the actual bundle structure per the judging guidelines, the claimed one-level-deep split is undelivered and navigation dead-ends. Anchor 2 fits (structure present in intent but effectively non-functional); anchor 3 would require working but poorly signaled references.

Specificity

Names the domain ('Test-driven development') and gestures at actions ('build features or fix bugs test-first') but lists no concrete skill actions such as write-failing-test, implement, refactor. Not score 4 because there is no list of several specific actions; not score 2 because the actions named are not purely generic.

Completeness

Both 'what' and 'when' are present, with an explicit 'Use when...' clause carrying concrete triggers, but the 'what' is a bare noun phrase ('Test-driven development.') with no elaboration of the actions performed. Matches anchor 4 ('when' explicit, 'what' present but thinner than the anchor-5 multi-action formulation).

Trigger Term Quality

Includes natural user phrases — 'build features', 'fix bugs', 'test-first', 'red-green-refactor', 'integration tests'. Falls short of anchor 5 because common synonyms like 'TDD', 'write tests first', and 'unit testing' are missing; better than anchor 3 because several natural trigger terms are covered.

Distinctiveness Conflict Risk

'Test-driven development' plus 'test-first', 'red-green-refactor', and 'integration tests' carves a distinct niche, but the broad lead-in 'build features or fix bugs' creates minor overlap risk with general coding skills if the 'test-first' qualifier is missed. Anchor 4 ('mostly distinct; minor overlap risk with closely related skills') is the best fit.