Conciseness

The ~45-line body is lean and assumes Claude's competence throughout: it never explains what a diff, grep, or teardown is, and every line carries instruction weight (e.g. 'Listing the callers is not the job. The agent can grep those in a second. The job is the breakage grep won't show you.'). This matches anchor 5 ('Lean and efficient; assumes Claude's competence; every token earns its place'); not 4 because there is no padded or over-explanatory passage that would need trimming — the brief framing sentences ('A blast-radius writeup that sounds right is worthless') justify a rule rather than padding.

Actionability

For an instruction-only skill the guidance is largely concrete: a 5-level evidence ladder ('You ran it. A script or test that calls the real code and fails loud if you're wrong'), a recipe for step 4 ('one small script that imports the same library the app ships and calls the exact function you're worried about'), and a specific output checklist. Not 5 because a few directions stay abstract (e.g. 'Work out when things run: microtasks, unmount and teardown, Solid versus React' — hints rather than executable steps, and oddly specific to Solid/React); not 3 because nothing is pseudocode-level and the key operations (read diff, find safety fact, write and run a proof script, paste output) are directly executable.

Workflow Clarity

The 6 'Steps' are clearly sequenced (read change → find the safety fact → look where grep stops → assess risks → prove the fact → fan out for big changes) with an explicit validation checkpoint ('Write a script or test that runs the real code, run it, and paste what happened') and a failure path ('If you couldn't prove it, write unproven'). This fits anchor 4 ('Clear sequence with most checkpoints present; minor validation gaps'). Not 5 because there is no fix-and-retry feedback loop and the evidence ladder, the steps, and the handback checklist are three parallel structures the reader must merge themselves; not 3 because validation is explicitly present, not missing or implicit.

Progressive Disclosure

No bundle files exist (no references/, scripts/, or assets/), and the self-contained body is under 50 lines with well-organized sections ('Don't trust your own writeup', 'How sure are you', 'Steps', 'What to hand back') — squarely the simple-skill case the rubric says can score 5 on organization alone. All cross-references are to sibling skills (`how`, `why`, `unslop`, `arena`), not nested files, so there is no reference depth or navigation problem. Not 4 because nothing that belongs in a separate file is inlined and no organization gaps exist.

Specificity

The description names the domain (finding downstream breakage from a change) and two concrete actions — "Find what a change could break somewhere else before it ships, beyond the diff" and "prove the one fact it's safe because of by running real code" — but coverage is not comprehensive (no mention of e.g. risk assessment or cleared-items output). This matches anchor 3 ("Names domain and 1-2 concrete actions, but not comprehensive"); not 4 because it does not list several distinct specific actions, and not 2 because the actions are concrete rather than minimal or generic.

Completeness

Both halves are explicit: the 'what' is "Find what a change could break somewhere else before it ships... and prove the one fact it's safe because of by running real code", and the 'when' is "Use for 'blast radius of X', 'what could this break', or reviewing a small diff you don't trust". This matches anchor 5 (clearly and explicitly answers both what AND when with concrete trigger phrases). Not 4 because the 'when' clause is fully explicit with quoted trigger phrases rather than merely present.

Trigger Term Quality

Trigger phrases "blast radius of X", "what could this break", and "reviewing a small diff you don't trust" are natural things a user would actually say, giving good keyword coverage. Not 5 because common synonyms and variations are missing (e.g. "impact analysis", "what does this affect", "downstream effects", "ripple effect"); not 3 because the included phrases go beyond 'some relevant keywords' — they read like real user utterances, including the exact trigger phrase 'blast radius of X'.

Distinctiveness Conflict Risk

The 'blast radius of X' / 'what could this break' framing carves out a clear niche with distinct triggers, and the emphasis on proving safety facts by running code differentiates it from plain review skills. Not 5 because "reviewing a small diff you don't trust" has minor overlap with general code-review/diff-review skills; not 3 because the primary triggers are specific and unlikely to fire for unrelated skills.