Conciseness

The body is lean and assumes Claude's competence: it never explains what TDD or red/green is, and every clause carries a rule ('a test that cannot fail is not a test', 'reproduction before theory'). No padded sections or known-concept explanations to trim, matching the 'every token earns its place' anchor.

Actionability

Gives concrete, executable directives ('Write the next test at a seam. Run it.', 'Implement the smallest change that turns it green', 'Substitute at the seam's declared boundary class only') plus a concrete output contract. Not a 5 because key dependencies are undefined in-skill: 'C2's approved output', 'the class C2 records', and 'the repair worker' refer to external artifacts and roles the reader must already know about.

Workflow Clarity

The loop is a clearly sequenced numbered workflow with an explicit validation checkpoint ('Watch it fail for the reason you expect') and a defined exception path ('If the behavior cannot be tested at any approved seam, stop and say so') with a reporting destination. Refactoring is explicitly excluded from the loop, removing ambiguity about scope.

Progressive Disclosure

The skill is under 50 lines with no need for external reference files (none exist in the bundle), and content is well-organized into clear sections (The loop, Rules, When no seam fits, Output). Per the simple-skill guideline, this satisfies the top anchor with well-organized sections alone.

Specificity

Lists several concrete actions — 'one test, one implementation', 'tracer-bullet red/green', 'independent expected values', 'substitutions only at the seam's boundary class' — but coverage is not fully comprehensive: 'launch Phase 4 reference' names no concrete action and reads as an insider pointer.

Completeness

The 'what' is clear (test-first loop with expected-value and substitution rules), but there is no 'Use when...' clause or equivalent explicit trigger guidance; 'launch Phase 4 reference' only weakly implies when, which caps completeness at 3 per the judging guidelines. Not a 2 because the 'what' half is concrete and multi-part.

Trigger Term Quality

'test-first' and 'red/green' are phrases a user might say, but common variations like 'TDD', 'unit test', or 'write a failing test' are missing, and the description is dominated by jargon ('pre-agreed seams', 'boundary class', 'tracer-bullet') that users would not naturally say. Not the level above because keyword coverage is partial rather than good.

Distinctiveness Conflict Risk

The seam-disciplined test-first framing carves a mostly distinct niche unlikely to trigger for unrelated skills, though bare 'test'/'implementation' terms leave minor overlap risk with general testing skills. Not a 5 because the description lacks explicit distinct trigger phrases that separate it from neighboring test-writing skills.