Conciseness

The body assumes Claude's competence — it never explains TDD, git, or what a PR is — and every sentence carries project-specific information (the commit-gate/landing-gate behavior, PGlite-based tests, the coverage/mutation commands). It is lean with no padded sections, matching the 5 anchor.

Actionability

Most steps are executable with concrete commands (`npm run check`, `npm run coverage:diff`, `npm run mutate:diff`, `git push -u origin <branch>`, `gh pr create --fill`), but the project-specific issue-CLI handoff in step 5 ('Hand the baton to it through the issue CLI') gives no command or example. That minor gap fits the 4 anchor rather than the fully copy-paste-ready 5.

Workflow Clarity

The five numbered sections give a clear sequence with explicit validation checkpoints: watch the failing test fail, run check 'until it's clean', confirm coverage and mutation scores, and a feedback loop for failure ('if it fails it blocks the commit and hands you the errors — fix them, don't work around the gate'). This matches the 5 anchor's explicit validation and error-recovery loop.

Progressive Disclosure

The ~55-line body keeps everything appropriately inline at this size, is organized into clearly headed stages, and delegates detail that belongs elsewhere via well-signaled pointers to the create-service and babysit-pr skills. No bundle files exist and none are needed; navigation is easy, matching the 5 anchor.

Specificity

The description enumerates multiple concrete actions — 'red-green TDD, making `npm run check` pass, committing on a branch, pushing, and opening a PR' plus shepherding 'through CI, reviews, and the merge' — comprehensively covering the feature loop. Coverage is complete rather than having minor gaps, so it matches the 5 anchor rather than 4.

Completeness

It explicitly answers both questions: 'what' via the enumerated loop 'from first failing test to an open, mergeable PR' and 'when' via the explicit trigger clause 'Use whenever building or changing a feature in Skylark'. Both are concrete and explicit, matching the 5 anchor.

Trigger Term Quality

'Use whenever building or changing a feature' is a natural phrase users would say, supported by terms like test, commit, push, and PR. Common synonyms and variations ('implement', 'add X', 'open a PR') are missing, which fits the 4 anchor (good coverage, a few natural terms missing) rather than the comprehensive 5.

Distinctiveness Conflict Risk

The skill is scoped to a clear niche (the build-to-open-PR loop in Skylark) and explicitly disambiguates its closest neighbor: 'Once the PR is open, hand off to the babysit-pr skill'. Because the boundary with the overlapping sibling skill is explicitly drawn, conflict risk is minimal, matching the 5 anchor.