Conciseness

The ~20-line body is lean and assumes Claude's competence: no explanations of what auth or sessions are; every token is a test instruction ('logout invalidates the session server-side', 'tampered signature, alg:none, wrong issuer or audience'). Matches the 5 anchor ('lean and efficient; every token earns its place'); there is nothing to trim, so it is not a 4.

Actionability

Guidance is concrete and executable despite being instruction-only (per scoring_notes, absence of code is not penalized when guidance is actionable): 'changing IDs in the URL, body, and GraphQL variables. Expect 403/404 with no data in the body', 'repeat the request at least 3 times before and after; 5xx never decides the result', 'cookie flags (HttpOnly, Secure, SameSite)'. Specific cases, methods, and expected outcomes cover the common cases — the 5 anchor. It is not a 4 because there are no minor gaps in concrete direction.

Workflow Clarity

Setup ('two customer accounts (A and B), an admin, and a signed-out browser') followed by a clear 7-step numbered sequence, each step with expected outcomes serving as validation ('Expect 403/404 with no data in the body', the stable-probe rule with '5xx never decides the result'), plus an explicit exit criterion checklist ('The matrix of role × object × action is complete with statuses'). This is not a destructive or batch operation, so no cap applies, and the validation/explicit-exit-criteria structure fits the 5 anchor better than the 4 anchor's 'minor validation gaps'.

Progressive Disclosure

No bundle files exist (references/, scripts/, assets/ are absent), and none are needed at ~20 lines. Per the judging guideline, a skill under 50 lines with no need for external references can score 5 with well-organized sections — which this has (Procedure, Rules, Exit criteria). Not a 4, since there are no organization gaps or misplaced content.

Specificity

The description enumerates many concrete testing actions and objects: 'Test authentication, sessions, roles, multi-tenant isolation, and object-level authorization, including IDOR, token tampering, magic links, and private content leakage through feeds, search, caches, and storage URLs' — comprehensive coverage with named vulnerability classes and leak vectors. It matches the 5 anchor (multiple specific concrete actions, comprehensive) and exceeds the 4 anchor, which allows minor coverage gaps.

Completeness

Both parts are explicit: the 'what' is 'Test authentication, sessions, roles, multi-tenant isolation, and object-level authorization...' and the 'when' is the explicit trigger clause 'Use for any app with accounts or private data'. This mirrors the 5 anchor ('clearly and explicitly answers both what AND when with concrete trigger phrases'); it is not a 4, since the 'when' clause is explicit and concrete rather than vague or only implied.

Trigger Term Quality

Good natural keyword coverage — 'authentication', 'sessions', 'roles', 'IDOR', 'token tampering', 'accounts', 'private data' are phrases a user testing auth would say — but common variations like 'login', 'access control', 'permissions', or 'authorization' (only 'authorization' appears, as 'object-level authorization') are partly missing. Fits the 4 anchor (good coverage, a few natural terms missing) rather than 5 (which expects synonyms and extensions); better than 3, which requires missing common variations.

Distinctiveness Conflict Risk

It carves out a clear niche — auth/access-control testing with distinct triggers like 'IDOR', 'token tampering', 'magic links', 'multi-tenant isolation' — that no generic skill would claim. Minimal conflict risk, matching the 5 anchor rather than the 4 anchor's 'minor overlap risk with closely related skills'.