Conciseness

Lean, rule-dense sections with no explanation of basic Swift concepts; every section instructs rather than describes. Not 5 because the Common Mistakes and Review Checklist sections partially restate the rule sections (e.g., Boolean assertion naming and type-repeating labels appear twice), which could be tightened.

Actionability

Concrete, immediately applicable guidance throughout: specific identifier examples ("sort()", "sorted()", "union(_:)" / "formUnion(_:)", "isEmpty", "remove(item)" vs "remove(element: item)"), a first-applicable-rule decision table for label strategy, and concrete bad examples in Common Mistakes. As an instruction-only skill whose specific examples cover the common cases, it meets the top anchor.

Workflow Clarity

A single-purpose guidelines/review skill with a clear decision procedure ("Use the first applicable rule") and a Review Checklist that serves as validation checkpoints. Not 5 because there is no explicitly ordered workflow for conducting a review pass (e.g., when to apply which section), and the skill exceeds the simple under-50-line exception.

Progressive Disclosure

The body is a concise overview with four one-level-deep references (all verified to exist in references/), each clearly signaled in its section with when-to-read guidance, plus a References index. Content is appropriately split: rules inline, extended examples and edge cases in the bundle files.

Specificity

Lists five concrete capability areas ("names, argument labels, mutating/nonmutating pairs, protocols, and documentation comments") within the Swift API design domain. Not 5 because the action is a single generalized verb ("Apply") applied to targets, whereas the 5 anchor shows multiple distinct concrete actions.

Completeness

Explicitly answers both questions: what ("Apply Swift API Design Guidelines to names, argument labels, mutating/nonmutating pairs, protocols, and documentation comments") and when ("Use when designing or reviewing Swift APIs for clarity at the call site") with concrete trigger phrasing. Not 4 because the 'when' clause is explicit and specific rather than generic.

Trigger Term Quality

Natural phrases like "designing or reviewing Swift APIs" and "clarity at the call site" plus specific terms ("argument labels", "protocols", "documentation comments") give good coverage. A few natural variations users might say (e.g., "naming", "Swift naming conventions") are missing, so it falls short of the 5 anchor's comprehensive synonym coverage.

Distinctiveness Conflict Risk

Clear niche (Swift API design guidelines) with an explicit boundary statement ("file and project organization belongs to the relevant architecture/UI skill") that actively routes away overlapping requests. Minimal conflict risk with sibling skills.