Conciseness

The Core Rules, Implementation Phase, and Final Evaluation are dense and prescriptive, but the opening paragraph explains TDD philosophy Claude already knows ("TDD is a design technique that uses tests as a tool. Design emerges from usage, not speculation..." and "it's crucial to be thorough and only add what tests demand") — minor over-explanation that could be trimmed. Not score 5, but well above anchor 3's "some unnecessary explanation" since the padding is confined to one paragraph.

Actionability

Concrete, executable instruction throughout: exact announcement strings ("Using TDD skill in mode: [auto|human]", "Starting refactoring stage", "Refactoring complete"), a worked [TEST] comment example, the given-when-then test format, the two-step red phase, and a per-line justification question ("Does a failing test require this?"). Per the scoring notes, an instruction-only skill needs concrete guidance rather than code, and this delivers it; specific examples cover the common cases.

Workflow Clarity

The sequence is explicit with validation checkpoints at every turn: predict-fail → run → observe → minimal fix (steps 3-10 of Implementation Phase), "Run all tests every time - Not just the one you're working on", "Run tests after each simplification", and feedback loops in Final Evaluation ("start the process for the missing tests from the beginning... go back to previous stages if needed"). This matches the anchor-5 pattern of explicit validation steps plus error-recovery loops; no destructive/batch cap applies.

Progressive Disclosure

The body is a concise process overview with two well-signaled, one-level-deep references that both exist: "For layered architectures, see [boundary-testing.md](references/boundary-testing.md) for L3/L4 altitude testing, property-based tests with fast-check..." and "walk through [ZOMBIES](references/zombies.md)". Neither reference file nests further references, content is appropriately split, and navigation is easy.

Specificity

"red-green-refactor cycles", "integration tests at service boundaries", and "property-based testing" name multiple specific concrete techniques that comprehensively cover the TDD workflow. It is not merely naming the domain like the score-4 anchor's "minor gaps" — the three techniques span the cycles, boundary scope, and test style completely.

Completeness

It explicitly answers what ("Test-driven development workflow using red-green-refactor cycles with integration tests at service boundaries and property-based testing") and when ("Use when the user explicitly requests TDD, test-first development, write tests first, unit tests, red-green-refactor, or property-based testing"), with concrete trigger phrases — exactly the anchor-5 pattern.

Trigger Term Quality

The trigger list "TDD, test-first development, write tests first, unit tests, red-green-refactor, or property-based testing" covers natural user phrasings with synonyms (TDD acronym plus the spelled-out "Test-driven development" in the what-clause, test-first/write-tests-first variants). This matches the comprehensive-with-synonyms anchor; file extensions do not apply to a process skill.

Distinctiveness Conflict Risk

The TDD/test-first/red-green-refactor niche is distinct, but the bare trigger term "unit tests" could fire for ordinary unit-test writing requests that are not TDD, a minor overlap risk with a general testing skill. Not score 5 ("minimal conflict risk") because of that one broad trigger; clearly above anchor 3 since the remaining triggers are highly specific to this methodology.