Conciseness

The body is dense with rules and GOOD/BAD examples and never explains basics Claude already knows, but there is trimmable redundancy: the ~28-line Review Checklist ("First argument follows the correct label rule…", "Mutating methods use imperative verb form") restates rules already stated in the preceding sections, and the Contents TOC duplicates section headers. This fits the score-4 anchor (efficient, minor instances that could be trimmed) rather than 5, whose "every token earns its place" standard the checklist duplication violates; it is well above 3 because there is no padded or unnecessary explanation.

Actionability

Guidance is fully concrete: decision tables with specific examples ("Omit label, merge words into base name | addSubview(y)"), copy-paste-ready Swift snippets for every rule ("array.sort()", "employees.remove(at: position)"), GOOD/BAD contrast pairs, and explicit decision procedures ("Apply the first matching row"). This matches the score-5 anchor (specific examples cover the common cases) and exceeds score 4 because no key detail is left abstract.

Workflow Clarity

The skill defines clear execution structure for a single-purpose review/design task: routing guidance at the top ("route language/type-system work to swift-language…"), a precedence-ordered decision table ("Apply the first matching row"), per-section "Load … when …" conditions, and a grouped Review Checklist (Argument Labels, Naming Semantics, Documentation, Conventions) that serves as explicit verification checkpoints. Per the simple-skill exception, the single action is unambiguous and checkpoints are present, so it meets the score-5 anchor rather than 4; no destructive or batch operations exist that would impose a cap.

Progressive Disclosure

Structure is exemplary: core rules inline in SKILL.md, four verified one-level-deep reference files (argument-labels-and-parameters.md, naming-and-clarity.md, side-effects-and-mutating-pairs.md, conventions-and-special-rules.md) each linked from its own section with a load condition ("Load [Argument Labels and Parameters]… when resolving abstraction boundaries…") and summarized again in a References section. All referenced paths and the -ed/-ing decision-tree anchor resolve to real files, and no reference nests further references, matching the score-5 anchor exactly.

Specificity

The description lists multiple specific concrete actions with comprehensive coverage: "name, label, and document Swift APIs" plus enumerated sub-capabilities such as "prepositional phrase rule", "-ed/-ing participle pattern, form- prefix, sort/sorted, formUnion/union", "O(1) complexity rule", and "default arguments over method families". It clearly matches the score-5 anchor (multiple specific concrete actions, comprehensive) rather than score 4 (minor gaps in coverage), as no significant guideline area is omitted.

Completeness

Both questions are answered explicitly and concretely: the "what" is the detailed capability enumeration ("Covers argument label rules… mutating/nonmutating pair naming… side-effect naming…"), and the "when" is the explicit clause "Use when designing new Swift APIs, reviewing naming and argument labels, writing documentation comments, or refactoring for call site clarity". This matches the score-5 anchor verbatim in structure; it is not score 4 because the when-clause is fully specific rather than improvable.

Trigger Term Quality

Natural trigger phrases a user would actually say are comprehensively covered: "designing new Swift APIs", "reviewing naming and argument labels", "writing documentation comments", "refactoring for call site clarity", plus synonyms like "naming", "casing conventions", "documentation comment". It sits at the score-5 anchor rather than 4 because the phrasing spans the full range of natural user requests for this domain with no notable missing synonyms (file extensions do not apply to a non-file skill).

Distinctiveness Conflict Risk

The description occupies a clear niche (Swift API design guidelines) with distinct triggers like "argument labels", "mutating/nonmutating pair naming", and "Swift APIs". It is narrowly scoped to API naming/labeling/documentation rather than general Swift language work, so conflict risk with adjacent skills (e.g., general Swift language or lint skills) is minimal — matching the score-5 anchor, not score 4's "minor overlap risk with closely related skills".