Conciseness

Every line carries non-obvious, project-specific knowledge Claude would not have ("the build succeeds while the binary still runs the OLD JS", "a second one blocks on the build lock and looks like a runtime hang"). There is no padding and no explanation of concepts Claude already knows; nothing to trim. Not 4 — no over-explanation exists anywhere in the body.

Actionability

Fully executable, copy-paste-ready commands throughout: `bun bd --version`, `bun bd -e '<repro>'`, `PATH="$HOME/.cargo/bin:$PATH"`, `touch src/jsc/bindings/InternalModuleRegistry.cpp`, `./build/debug/bun-debug <file>`, `node -e '<same repro>'` — each gotcha paired with its specific fix. Common cases (JS-visible changes, workers/subprocesses, node:cluster, Node-compat) are all covered. Not 4 — no gaps in concrete guidance.

Workflow Clarity

The flow is unambiguous — build, then drive — and the first gotcha supplies an explicit validation checkpoint with a feedback loop: "Gate on the binary, not the build: ask the binary you just built — `bun bd -e 'console.log(<Class>.toString().includes("<new-id>"))'`... If false, `touch src/jsc/bindings/InternalModuleRegistry.cpp` and rebuild." The Gotchas section doubles as a checklist of pitfalls. Not 4 — validation and recovery steps are explicit, not merely present.

Progressive Disclosure

This is a single-task skill under 50 lines with no bundle files (references/, scripts/, assets/ are absent), so everything appropriately lives inline in three well-organized sections (Build, Drive, Gotchas). Per the rubric's simple-skill note, well-organized sections alone earn a 5 here. Not 4 — no content is misplaced or in need of splitting.

Specificity

"Verify a Bun runtime change" names the domain and "by driving the debug binary end-to-end" gives a concrete method, but only one action is described rather than several. Not 2 (the action and method are concrete, not generic like "Processes PDF files"); not 4 (no list of several specific actions such as build, run repro, cross-check).

Completeness

The "what" is clear ("Verify a Bun runtime change by driving the debug binary end-to-end") but there is no "Use when..." clause or equivalent explicit trigger guidance, so completeness is capped at 3. It fits anchor 3 exactly: clear what, when missing or only weakly implied.

Trigger Term Quality

Relevant keywords are present ("Verify", "Bun runtime change", "debug binary"), but common variations users would actually say — "test", "reproduce", "check my change" — are missing. Not 2 (the terms are domain-relevant, not generic); not 4 (natural synonyms and artifacts like `bun-debug` or `bun bd` are absent).

Distinctiveness Conflict Risk

"Bun runtime change" and "debug binary" carve a clear niche with minimal overlap risk among plausible skills. Not 5 because the bare verb "Verify" is generic and could weakly match unrelated verification/testing skills; not 3 because the domain terms are far more specific than "Works with document files".