Conciseness

The body is lean with no padding of concepts Claude already knows; every section is task-relevant. However, "Check" and "Code Review" are near-duplicates ("Flag blocked paste, password-manager hostility, manual transcription requirements..." appears in substance in both), which is a minor instance of content that could be tightened. Fits anchor 4 rather than anchor 5's every-token-earns-its-place.

Actionability

Gives concrete, specific guidance for a review skill: exact flags (blocked paste, password-manager hostility, manual transcription, inaccessible OTP handling, CAPTCHA without alternative), concrete fix directions (password-manager-friendly fields, paste and OTP autofill, "autocomplete=\"one-time-code\""), and named alternative paths (passkeys, magic links, device approval). Per the rubric's instruction-only note, absent code is not penalized, but detection specifics (e.g., what a paste-block handler looks like) are deferred to the reference, matching anchor 4's minor gaps.

Workflow Clarity

The single review purpose is unambiguous and organized as Quick Reference, Check, Fix, Explain, Code Review — a clear review workflow. It falls short of anchor 5 because the body contains no explicit verification checkpoint for findings; the verification guidance exists in references/rule.md but is not signaled from the body, leaving the validate step implicit.

Progressive Disclosure

The body is a concise, well-sectioned overview that delegates full implementation details, code examples, and framework-specific guidance to a clearly signaled one-level-deep pointer ("see references/rule.md"), and that file exists and carries exactly that content. This matches anchor 5's clear overview with well-signaled one-level-deep references and easy navigation.

Specificity

Names concrete review targets ("sign-in, sign-up, MFA, CAPTCHA, recovery, and re-auth flows") and a specific action ("Evaluate the full authentication path, including error handling and backup methods"), giving several specifics, though it relies on essentially one action verb. Not 3 since more than 1-2 concrete actions/targets are named; not 5 since it is not a comprehensive list of distinct actions.

Completeness

Explicitly answers both: what ("Evaluate the full authentication path, including error handling and backup methods, not just the primary login form") and when ("Use when reviewing sign-in, sign-up, MFA, CAPTCHA, recovery, and re-auth flows") with concrete trigger phrases. The 'when' clause is fully explicit and specific, so anchor 4's caveat ('when' could be more explicit) does not apply.

Trigger Term Quality

Includes natural terms users would say ("sign-in", "sign-up", "MFA", "CAPTCHA", "recovery", "re-auth", "login"), but misses common variations like "two-factor", "2FA", "OTP", and "password reset". Clearly above anchor 3 (relevant keywords present), just short of anchor 5's comprehensive synonym coverage.

Distinctiveness Conflict Risk

Has a clear authentication-accessibility niche with distinct triggers, but "reviewing sign-in, sign-up, MFA" flows could overlap with a general security-review skill targeting the same flows. Minor overlap risk with closely related skills matches anchor 4 rather than anchor 5's minimal conflict risk.