Conciseness

The body doesn't explain basics Claude already knows and the Anti-Rationalization table carries genuinely non-obvious Swift 6.2 specifics, but the same symptom-to-file routing is restated in four formats (Quick Reference table, dot graph plus numbered Decision Tree, Critical Patterns, Example Invocations). That is more than 'some' unnecessary duplication, yet not severe padding, matching the 3 anchor ('mostly efficient but could be tightened').

Actionability

Routing guidance is concrete and executable ('Read: skills/isolation-inheritance-diag.md', '/axiom:audit concurrency', 'xcprof analyze --start-ms/--end-ms --user-binary') with user-example mappings covering common cases. It falls short of 5 because the referenced skills/*.md files are not present in the provided bundle, so the primary instruction cannot be verified to resolve.

Workflow Clarity

The routing workflow is a clear, well-sequenced decision tree, and the Conflict Resolution section provides explicit ordering checkpoints ('Try concurrency FIRST — Main thread blocking is the #1 cause... Only use axiom-performance if concurrency fixes don't help'). It is not a 5 because there is no guidance for the case where no branch matches, and the duplicated routing formats add mild ambiguity about which list is authoritative.

Progressive Disclosure

The skill is structured as a clean overview router with one-level-deep, symptom-indexed references, which fits the 5 anchor's shape. However, the referenced paths (skills/swift-concurrency.md etc.) are not part of this bundle (no references/ or skills/ files provided) and their base location is only indirectly defined via the '<plugin-root>' indirection, so navigation cannot be fully verified — matching the 4 anchor's 'minor organization gaps'.

Specificity

The description enumerates several specific coverage areas ('Covers Swift 6 concurrency, @MainActor, Sendable, data races, async/await patterns'), which exceeds the 1-2 concrete actions of the 3 anchor. It stays at 4 rather than 5 because these are topic labels rather than concrete actions (e.g., 'diagnose runtime isolation crashes', 'migrate DispatchQueue to actors'), leaving minor gaps in capability coverage.

Completeness

It explicitly answers 'when' with concrete triggers ('Use when writing ANY async code, actors, or threads in an Apple-platform app, or seeing ANY concurrency error') and answers 'what' via scope ('Covers Swift 6 concurrency, @MainActor, Sendable, data races, async/await patterns'). It is not a 5 because the 'what' states topics covered rather than what the skill does with them, matching the 4 anchor's 'when' could be more explicit / what less action-oriented.

Trigger Term Quality

Natural user phrases are well covered: 'async code', 'actors', 'threads', 'concurrency error', 'data races', 'async/await' — all things a user would actually say. It falls short of the 5 anchor because common variations like 'main thread blocking', 'thread-safe', 'Task', or 'background thread' are absent.

Distinctiveness Conflict Risk

The description is scoped to 'an Apple-platform app' and uses platform-specific terms (@MainActor, Sendable, Swift 6), establishing a clear niche with distinct triggers and minimal conflict risk with generic skills.