Conciseness

The 70-line body is pure procedural directives with no explanation of concepts Claude already knows (no 'what is the Language Detector API' preamble) and no padded sections; even the non-obvious notes ('Treat availability() as a capability check, not a guarantee...') carry real domain knowledge. It matches the 5 anchor (lean, assumes Claude's competence, every token earns its place) rather than the 4 anchor, since nothing needs trimming.

Actionability

Guidance is fully concrete throughout: an executable command ('node scripts/find-language-detector-targets.mjs .'), exact file reads ('Read references/language-detector-reference.md', 'Read assets/language-detector-session.template.ts'), and exact API calls (LanguageDetector.availability(), create(), detect(), measureInputUsage(), destroy(), AbortController). Per the rubric's scoring note, the absence of inline code in this instruction-only skill is not penalized because the guidance is specific and actionable, placing it at the 5 anchor rather than the 4 anchor.

Workflow Clarity

Five clearly sequenced steps with stop-and-ask checkpoints ('stop and ask which app should receive...'), an explicit validation step (Step 5 re-runs the inventory script, tests a create()+detect() flow, and runs build/typecheck/tests), and an Error Handling section that maps specific exceptions (NotAllowedError, InvalidStateError, QuotaExceededError) to concrete recovery actions — a feedback loop. This matches the 5 anchor (explicit validation steps, feedback loops for error recovery) rather than the 4 anchor.

Progressive Disclosure

The body is a lean 70-line overview; the four references, one script, and one asset template all exist on disk, are referenced with clear condition signals ('Read references/examples.md when the feature needs...'), and are one level deep (the only cross-reference is a lateral troubleshooting.md → compatibility.md pointer). This matches the 5 anchor (clear overview, well-signaled one-level-deep references, easy navigation) rather than the 4 anchor.

Specificity

The description names the domain ('browser Language Detector API integrations in JavaScript or TypeScript web apps') and lists many concrete actions — 'support checks, availability and model download flows, session creation, detect() calls, input-usage measurement, permissions-policy handling, or compatibility fallbacks' — covering both implementing and debugging. This matches the 5 anchor (multiple specific concrete actions, comprehensive coverage); it is above the 4 anchor because there are no minor gaps in capability coverage.

Completeness

It explicitly answers both parts: the 'what' is the first sentence ('Implements and debugs browser Language Detector API integrations...') and the 'when' is an explicit 'Use when adding...' clause with concrete trigger phrases, plus a 'Don't use for' exclusion. This matches the 5 anchor exactly; the 4 anchor requires a 'when' that could be more explicit, which does not apply here.

Trigger Term Quality

Natural trigger terms a user would say are comprehensively covered: 'LanguageDetector', 'detect() calls', 'built-in language detection', 'model download', 'availability', 'compatibility fallbacks'. No file extensions are relevant to a browser API, and no common synonym or variation of the trigger phrasing is missing, so it sits at the 5 anchor rather than the 4 anchor ('a few natural terms missing').

Distinctiveness Conflict Risk

The explicit exclusion list — 'Don't use for server-side language detection SDKs, cloud translation services, or generic NLP pipelines' — fences off the nearest confusable skills, giving a clear browser-API niche with distinct triggers and minimal conflict risk, matching the 5 anchor rather than the 4 anchor ('minor overlap risk with closely related skills').