Conciseness

The ~370-line body avoids known-concept padding and nearly every paragraph encodes a genuine Lean-project failure mode (sorryAx on the dependency chain, conditional lemmas vs. the target, compile-success of the wrong root module), but key principles are restated across sections 1, 2, and 5, reviewer routing rules appear in both the opening blockquote and three section-4 subsections, and generic honesty policy is woven throughout. Mostly efficient but could be tightened considerably, fitting the 3 anchor better than 2 (no padded explanations of things Claude already knows) or 4 (repetition exceeds minor trimming).

Actionability

Concrete guidance throughout: an entry-state decision table, an interface ledger table, a 7-step implementation loop with specific actions ("Test unfamiliar declarations locally with `#check`", "Compile the affected module; after integration, compile the downstream target"), a worked example type (`Certificate x → Desired x`), a final-evidence checklist, and a fill-in continuation-note template. As an instruction-only skill this is actionable, but the copy-paste commands (lake build, #print axioms) live one hop away in references, leaving minor gaps that keep it below the 5 anchor.

Workflow Clarity

Clear sequence (sections 1–6 with an ASCII core-workflow diagram), explicit A/B/C validation checkpoints with stated triggers, feedback loops ("Diagnose the first relevant error... Implement valid fixes, compile them, and request follow-up"), and a final verification checklist. The reviewer-routing overlay with pending/unavailable states and validation specifics deferred to references (exit-status checking, axiom printing) muddy the mainline flow, matching the 4 anchor rather than 5.

Progressive Disclosure

The three local references (adversarial-review.md, lean-working-loop.md, verification-and-handoff.md) all exist, are substantive, and are well-signaled with "read when" conditions — but three ../shared-references/*.md links do not resolve within this bundle, and substantial reviewer-routing and objection-handling policy is inlined in the body that belongs in adversarial-review.md. Structure is good but the body is not a lean overview, fitting the 3 anchor better than 4 (more than minor organization gaps) or 2 (references are clearly signaled, not buried).

Specificity

Lists multiple specific concrete actions covering the full lifecycle in third person: "Develop and verify a mathematical proof in Lean, continue an incomplete Lean project, or audit whether it proves the original statement", plus "Connect actual inputs to intermediate lemmas, assemble the target theorem, check its transitive axioms, and provide a reproducible handoff". Coverage is comprehensive with no minor gaps, matching the 5 anchor rather than 4.

Completeness

Explicitly answers both "what" (develop/verify, continue, audit, connect inputs, check transitive axioms, hand off) and "when" ("Use when Lean is requested or a specific proof obligation benefits from formal verification"). The "when" clause is explicit with concrete triggers, and it additionally routes ordinary drafting to proof-writer, matching the 5 anchor.

Trigger Term Quality

Core natural terms are present ("Lean", "formal verification", "Lean project", "mathematical proof") — the words a user requesting this skill would actually say. Missing common synonyms and file extensions such as ".lean", "Mathlib", "proof assistant", or "formalize", so it fits the 4 anchor (good coverage, a few natural terms missing) rather than the 5 anchor.

Distinctiveness Conflict Risk

Clear niche (Lean formal verification) with distinct triggers, and it actively disambiguates from the closest sibling skill ("use proof-writer for ordinary mathematical drafting"), minimizing overlap risk. Matches the 5 anchor (clear niche, distinct triggers, minimal conflict risk).