Conciseness

The 25-line body is tight: a numbered workflow, a six-item analysis checklist, and a report spec with no concept explanations Claude already knows. Not 5: the six analysis bullets partially duplicate the loaded reference's principle list, and phrases like "to ensure they are fully available in the context" could be trimmed.

Actionability

Guidance is concrete and executable throughout: which file to read, how to disambiguate the target (user-specified files, open file, or ask), named principles to check, and an explicit report format (letter grade, critical issues, suggestions, before/after code blocks) with a concrete artifact path. Not 5: no example report snippet or concrete naming for issue categorization; the artifact path convention is asserted without an example.

Workflow Clarity

The four steps (Load → Identify → Analyze → Report) are clearly sequenced, and the Identify step includes a fallback checkpoint ("If neither, ask the user to specify the target files"). Not 5: there is no validation checkpoint on the output (e.g., confirming the guidelines were found/loaded or that the report was saved), though this is a read-only review so no destructive-operation cap applies.

Progressive Disclosure

The under-50-line body is an overview that points to exactly one real, clearly signaled, one-level-deep reference ([references/canonical_api_design.md](references/canonical_api_design.md)), which exists in the bundle and is itself self-contained (a table of contents plus principle sections, no nested references). This matches the anchor for a clear overview with well-signaled one-level-deep references.

Specificity

"Reviews the specified code against the canonical API Design guidelines" names the domain and exactly one concrete action (reviewing code against a named guidelines corpus); the report structure (grade, issues, before/after examples) lives only in the body, not the description. This matches the anchor 'names domain and 1-2 concrete actions, but not comprehensive' — not 4, since it does not list several specific actions.

Completeness

The description states what it does ("Reviews the specified code against the canonical API Design guidelines") and when to use it with concrete trigger phrases ("Use this skill when the user asks for an API review or to check code against API design principles"), matching the top anchor's pattern. It is not 4 because the 'when' is explicit and gives multiple concrete trigger phrasings rather than being merely adequate.

Trigger Term Quality

"API review", "check code", and "API design principles" are natural phrases a user would say, giving good coverage. Not 5: common synonyms/extensions such as "API guidelines", "design review", or named artifact types (.dart, API spec) are absent.

Distinctiveness Conflict Risk

"API review" and "API design principles" carve out a clear niche distinct from generic code-review skills. Not 5: a bare request like "review this code" could plausibly route here, so there is minor overlap risk with closely related code-review skills.