Conciseness

The body is dense with novel, opinionated guidance (it does not re-teach concepts Claude already knows), but several sections could be tightened: the Codat/Weavr narrative war stories, the extended state/events prose, and the 'Applying this skill' section, which restates points already made in the component sections. This matches 'mostly efficient but includes some unnecessary explanation or could be tightened' (3) rather than 'minor instances of over-explanation' (4), and is well above generic padding (2).

Actionability

As an instruction-only design skill it provides concrete guidance: a copy-paste-ready `issues` JSON example, a field table with types/required/purpose, the explicit naming grammar `{domain}.{class}.{reason}`, parsing rules ('splitting on `.` and matching prefixes'), and per-scenario instructions ('enumerate the ways it can fail, map each to a namespaced `issue` code'). Mostly executable guidance with minor gaps — no inline worked end-to-end example, which is delegated to the references — so 4 rather than 5.

Workflow Clarity

No destructive or batch operations, so the validation cap does not apply. Each scenario in 'Applying this skill' has a clear sequence, and 'Reviewing an existing API' supplies a verification checkpoint ('check it against the seven principles and the field table' with enumerated common gaps). Clear sequence with most checkpoints present (4); not 5 because only the review path has an explicit check step and there are no feedback loops for the design paths.

Progressive Disclosure

The body is an overview that offloads full depth to five reference files, all of which exist in references/ (error-handling.md, event-status-design.md, view-vs-data-endpoints.md, auth-schemes.md, consuming-in-react.md). References are one level deep and well-signaled with purpose and read-when guidance ('Read it before finalising a schema or reviewing one in depth'), matching the top anchor for clear overview with well-signaled references and easy navigation.

Specificity

The description lists multiple specific capabilities — 'error and warning handling, resource state and lifecycle, read-endpoint structure, pagination, and authentication' — down to component-level detail like 'cursor vs offset pagination' and 'security schemes, API keys vs bearer tokens, stepped-up tokens'. Coverage is comprehensive for the skill's stated scope and matches the body's actual components, so it sits at the top anchor rather than 'minor gaps' (4).

Completeness

Both 'what' (the five capability areas) and 'when' are explicit, with three concrete trigger formulations: 'Use when designing, reviewing, or implementing HTTP APIs', 'Triggers on error responses and formats, response envelopes, webhook payloads', and 'Apply whenever an API surfaces a failure, state change, view of data, or auth requirement to a client'. This clearly matches the top anchor; it is not 4 because the 'when' is explicit and specific rather than merely present.

Trigger Term Quality

Good natural-term coverage ('error responses', 'webhook payloads', 'state machines', 'status fields', 'API keys vs bearer tokens'), but a few phrases users would naturally say are missing — 'REST', 'error codes', 'HTTP status codes'. This fits 'good keyword coverage; a few natural terms missing' (4) rather than comprehensive synonym coverage (5), and is clearly above 'some relevant keywords but missing common variations' (3).

Distinctiveness Conflict Risk

A clear niche (opinionated HTTP API contract patterns) with distinct triggers, but broad terms like 'authentication' and 'pagination' carry minor overlap risk with closely related skills (e.g., a general REST/OpenAPI or security-review skill). Mostly distinct with minor overlap risk (4) rather than minimal conflict risk (5).