Lists multiple specific concrete actions: designing REST or GraphQL APIs, creating OpenAPI specifications, planning API architecture, resource modeling, versioning strategies, pagination patterns, error handling standards.

The 'when' is well-covered with explicit 'Use when...' and 'Invoke for...' clauses, but the 'what' is only implied through the trigger terms rather than explicitly stated. The description tells Claude when to use it but doesn't clearly state what the skill actually does (e.g., 'Guides API design decisions and generates specifications'). However, the 'Use when' clause is present and strong, so it narrowly misses a 3 due to the weak 'what' component.

Includes strong natural keywords users would say: 'REST', 'GraphQL', 'API', 'OpenAPI', 'versioning', 'pagination', 'error handling', 'resource modeling'. These cover common variations of how users would describe API design tasks.

The description carves out a clear niche around API design with distinct triggers like 'REST', 'GraphQL', 'OpenAPI specifications', 'pagination patterns', and 'versioning strategies' that are unlikely to conflict with other skills.

The skill is generally well-structured but the large OpenAPI template (~80 lines) is borderline excessive for inline content—it could be referenced from a separate file. The MUST DO/MUST NOT DO lists contain some items Claude would already know (e.g., 'use proper HTTP methods', 'don't ignore HTTP status code semantics'). The Knowledge Reference section at the bottom is a list of concepts Claude already knows and adds no value.

The skill provides fully executable, copy-paste-ready OpenAPI 3.1 YAML, a concrete RFC 7807 error response example, specific CLI commands for linting and mocking (`npx @redocly/cli lint`, `npx @stoplight/prism-cli mock`), and a clear output checklist. Guidance is concrete and specific throughout.

The core workflow is clearly sequenced with 6 numbered steps, includes an explicit validation checkpoint (step 4: lint before proceeding), a verification step (step 5: mock and test), and the output checklist reinforces that validation must pass. The feedback loop is implicit but the 'validate before proceeding' gate is clear.

The Reference Guide table with 'Load When' context is an excellent progressive disclosure pattern pointing to 5 reference files. However, no bundle files are provided, so these references are unverifiable. Additionally, the large OpenAPI template is inlined rather than being in a referenced file, which bloats the main skill body and would be better as a separate template file.