Conciseness

The body is efficient and assumes Claude's competence — bullets name exact APIs, paths, and patterns with no basic-concept padding (e.g., 'bind the handler once in the constructor... the two bindings won't match on removal'). It falls short of anchor 5 because content overlaps across Standing Conventions, Common Pitfalls, File-Glob Guidance, and the Review Checklist, so some tokens could be trimmed.

Actionability

Guidance is fully concrete and executable: exact commands ('mach lint --outgoing', 'mots clean'), platform APIs ('nsIIOService::hostnameIsLocalIPAddress', 'SpecialPowers.pushPrefEnv'), real file paths ('browser/locales/en-US/browser/ipProtection.ftl'), and copy-ready code patterns ('sandbox.stub(IPPProxyManager, "state").value(...)') covering the module's common review cases.

Workflow Clarity

This is a single-task reference skill (review IPP changes) with an unambiguous action and an explicit Review Checklist supplying validation checkpoints ('mach lint --outgoing' clean, accessibility verified, lifecycle balanced). It is below anchor 5 because there is no ordered review sequence or validate-fix-retry feedback loop, only an unordered checklist.

Progressive Disclosure

The skill is self-contained with no bundle files, and the body is well organized under clear section headers (Scope, Conventions, Campaigns, Pitfalls, File-Glob Guidance, Checklist) with each section earning its place. It does not reach anchor 5 because the overlapping conventions/pitfalls/file-glob/checklist sections could be consolidated or split out, a minor organization gap.

Specificity

The description names a specific domain ('Firefox's built-in IP Protection (VPN) module') and lists several concrete coverage areas ('panel UI, proxy/channel filtering, authentication, telemetry, and localization'). It stops short of anchor 5 because these are topical areas rather than a comprehensive list of concrete actions the skill performs.

Completeness

The 'what' is clear — durable review guidance for the IPP module and its covered areas — but there is no 'Use when...' clause or equivalent explicit trigger guidance; the 'when' is only weakly implied by the review-guidance framing. Per the rubric guideline, a missing 'Use when' clause caps completeness at 3.

Trigger Term Quality

Good keyword coverage with natural terms a developer would use ('Firefox', 'IP Protection', 'VPN', 'proxy', 'authentication', 'telemetry'). A few natural variations are missing (e.g., 'Mozilla', 'Mozilla Central', 'Guardian', 'VPN review'), so it does not reach anchor 5's comprehensive synonym/extension coverage.

Distinctiveness Conflict Risk

The description targets a clear niche (Firefox's built-in IP Protection VPN module) with distinct module-specific triggers, making it highly unlikely to fire for the wrong skill.