Conciseness

The core guidance is dense and information-bearing with almost no re-teaching of known concepts (e.g., 'use RFC 7807 Problem Details for REST where appropriate' is a pointer, not a tutorial). Not 5 because two framework-boilerplate sections (Base Framework policy links, Optional Workflow Integration) and a Routing Boundary section that repeats the description's exclusions consume roughly 15% of the body without adding API-specific value; not 3 because beyond that boilerplate nearly every token earns its place.

Actionability

For an instruction-only skill the guidance is highly concrete: an exact output-contract template ('Use this exact structure... Write **Not assessed - evidence needed: ...**'), specific review traces ('credential -> identity -> scope/role -> tenant -> resource ownership -> response fields'), named vulnerability classes (BOLA/IDOR, mass assignment), named tools (Spectral, Schemathesis, k6), specific headers (Cache-Control, ETag, Vary), and three worked example scenarios covering common cases. Not 4 because no key execution detail is missing for a review skill — the examples and checklists are copy-paste usable.

Workflow Clarity

A clearly sequenced six-step workflow (purpose/budgets -> style selection -> contract review -> security/tenancy -> reliability/scale -> version/validate/release) with explicit checkpoints: mandatory evidence/confidence labels (Verified/Likely/Assumption/Unknown), 'Test negative cases', 'Measure before recommending performance changes', a closing quality checklist, and validation gates in step 6 (contract tests, lint/spec-validate, fuzz, negative authorization tests, canary). This is a review skill, so the destructive/batch feedback-loop cap does not apply.

Progressive Disclosure

The three real reference files (references/protocols-and-async.md, references/rest-and-openapi.md, references/security-and-resilience.md) exist, are one level deep, and are clearly signaled inline. However, the Base Framework section marks nine 'Required packaged policies' at shared/base/*.md plus shared/workflow-contract.md, none of which exist in the bundle — ten dead paths — and scripts/validate_scenarios.py sits in the bundle unreferenced by the body. Not 4 because broken required references plus an orphaned script file are more than minor organization gaps; not 2 because the actual reference split and signaling of the files that do exist is well done.

Specificity

The description lists several concrete actions — 'Review or design an API contract', 'compatibility assessment', 'API-specific security/resilience guidance' — and covers the full protocol domain (REST, GraphQL, gRPC, events, webhooks, streaming, OpenAPI/AsyncAPI). Not 5 because the verbs remain high-level (review/design) rather than enumerating concrete tasks the way the top anchor's example does; not 3 because multiple actions plus full domain coverage exceed the 1–2 action bar.

Completeness

Both questions are answered explicitly: what ('Review or design an API contract: REST, GraphQL, gRPC, events, webhooks, streaming, or OpenAPI/AsyncAPI') and when ('Use when the primary deliverable is an interface contract, compatibility assessment, or API-specific security/resilience guidance'), plus negative boundary guidance ('Do not use for whole-system architecture planning, generic code review, database modeling, or implementation debugging'). Matches the anchor-5 example structure of concrete what + explicit when.

Trigger Term Quality

Natural terms users would say are present: 'review API', 'design an API contract', protocol names (REST, GraphQL, gRPC, webhooks, OpenAPI/AsyncAPI), 'compatibility', 'security/resilience'. Not 5 because common synonyms like 'Swagger', 'endpoints', or 'API audit' phrasing (only 'audit'-adjacent terms appear) have partial coverage; not 3 because coverage clearly goes beyond a couple of generic keywords.

Distinctiveness Conflict Risk

It carves a clear niche (API/interface contracts) and explicitly disambiguates adjacent skills ('Do not use for whole-system architecture planning, generic code review, database modeling, or implementation debugging'), which minimizes wrong-skill triggering. Not 4 because the exclusion list removes nearly all overlap risk with the most confusable neighbors.