Conciseness

The body is dense and assumes Claude's competence throughout — no basic concepts are explained — with occasionally motivational rationale ("The plan is the one artefact every later step inherits...") and illustrative war stories (the vite minify no-op, the GDPR erasure path) that add tokens beyond the bare rule. It fits anchor 4 (efficient, minor instances that could be trimmed) rather than 3, because the anecdotes function as calibration examples for judgment calls rather than true padding, and not 5 because some rationale sentences could be cut without losing instruction.

Actionability

The skill supplies a verbatim, copy-paste attacker prompt with one clearly marked adaptation point (the plan path), exact file and symbol references (`.claude/agents/attacker.md`, `tools/pr-metrics/index.ts`, `resolveDispatchBranch`), concrete skip/never-skip criteria, and a three-outcome closure procedure with an explicit label (`needs:decision`). For an instruction-only skill this is fully executable guidance, matching anchor 5.

Workflow Clarity

Steps 0-4 are clearly sequenced with an explicit gate ("No implementation starts while a finding is open. Silence is not a rejection."), a defined closure decision procedure, a re-run feedback loop tied to plan-shape changes, and a validation philosophy that demands observed failure ("Break the input, watch the non-zero exit"). This matches anchor 5 (clear sequence, explicit validation, feedback loops); anchor 4 would require missing checkpoints, which are not missing.

Progressive Disclosure

There are no bundle files (no references/, scripts/, or assets/), and the single-file body is well-sectioned (What this run must produce, Steps 0-4, Finish) with all external references (attacker.md, CLAUDE.md, the wiki, pr-metrics) clearly signaled and one level deep. It fits anchor 4 (good structure, minor organization gaps) rather than 5: the under-50-line simple-skill exception does not apply (~140 lines), and the 'Finish' section carries tangential forward-looking advice that slightly muddies the otherwise clean navigation.

Specificity

The description names the domain (implementation-plan verification) and two concrete actions — "hands the plan to a second model in a fresh context to attack it" and "requires every finding to be closed or rejected in writing" — but coverage is not comprehensive; skip criteria, escalation, and re-run behavior are absent. It fits anchor 3 (1-2 concrete actions, not comprehensive) better than anchor 4, which expects several listed actions with only minor gaps.

Completeness

It explicitly answers both questions: the "what" is concrete ("hands the plan to a second model in a fresh context to attack it, then requires every finding to be closed or rejected in writing") and the "when" opens with "Use when an implementation plan has just been written and before any code is written", reinforced with additional trigger context ("worth running on its own for any plan whose assumptions have not been checked"). This clearly matches anchor 5; anchor 4 would require the 'when' to be less explicit or specific, which it is not.

Trigger Term Quality

Relevant keywords are present ("implementation plan", "before any code is written", "assumptions have not been checked against the code"), but common natural variations a user would say — "review the plan", "red-team the plan", "challenge/critique the plan" — are missing. This matches anchor 3 (some relevant keywords, missing synonyms) rather than 4, which requires good coverage with only a few terms missing.

Distinctiveness Conflict Risk

The trigger is a narrow niche (adversarially reviewing a freshly written implementation plan before coding) with timing-specific conditions and explicit invokers ("Invoked by new-feat... and by orchestrate"), making wrong-skill triggering very unlikely. This matches anchor 5 (clear niche, distinct triggers, minimal conflict risk); anchor 4 would imply overlap with closely related skills, which the timing and invoker framing avoids.