Conciseness

The intro paragraph explains locale formatting differences Claude already knows ('a value formatted as "$1,234.56" in the US is written "1.234,56 $" in Germany'), and the same Intl.NumberFormat/DateTimeFormat/Collator guidance is repeated nearly verbatim across 'Quick Reference', 'Check', 'Fix', and 'Code Review'. It is mostly efficient but includes unnecessary explanation and could be tightened — matching the score-3 anchor rather than the minor-trimming score-4 anchor.

Actionability

The body names the exact APIs to use ('Intl.NumberFormat', 'Intl.DateTimeFormat', 'Intl.Collator', 'resolve a supported fallback locale') but contains no inline code, no detection patterns for manual formatting, and no example of a fallback chain — key execution details are all deferred to references/rule.md. This is concrete-but-incomplete guidance, matching the score-3 anchor ('missing key details') rather than the mostly-executable score-4 anchor.

Workflow Clarity

The Check → Fix → Explain → Code Review sequence is clearly laid out and unambiguous for this simple review skill, with each section stating exactly what to identify and replace. However, no verification checkpoint exists (e.g., confirming formatted output across multiple locales after fixing), which leaves minor validation gaps — the score-4 anchor rather than the explicit-validation score-5 anchor.

Progressive Disclosure

The body is a short, well-sectioned overview that correctly delegates implementation details to a real one-level-deep bundle file, clearly signaled as 'For full implementation details, code examples, and framework-specific guidance, see references/rule.md'. The reference is only signaled once at the bottom rather than from the sections where the details apply, a minor organization gap matching the score-4 anchor rather than the well-labeled-per-topic score-5 pattern.

Specificity

The description names its domain ('format numbers, prices, or dates', 'Intl APIs') and one composite action — 'check whether Intl APIs are used correctly' — but lists no further concrete actions such as flagging hardcoded symbols or showing alternatives. It matches the anchor 'names domain and 1-2 concrete actions, but not comprehensive' and falls short of the score-4 anchor, which expects several distinct specific actions.

Completeness

It explicitly answers both parts: 'when' via the concrete trigger phrase 'Use when reviewing utility functions, component props, or template strings that format numbers, prices, or dates', and 'what' via 'check whether Intl APIs are used correctly'. Both are explicit and concrete, matching the score-5 anchor; the score-4 anchor ('when' could be more explicit) clearly undersells the detailed trigger clause.

Trigger Term Quality

Natural terms are well covered: 'reviewing utility functions', 'component props', 'template strings', 'format numbers, prices, or dates', 'Intl APIs'. Common synonyms a user might say are missing ('currency', 'locale', 'i18n', 'internationalization'), so it fits 'good keyword coverage; a few natural terms missing' rather than the comprehensive score-5 anchor.

Distinctiveness Conflict Risk

The Intl/locale-formatting review niche is mostly distinct, but the opening 'Use when reviewing utility functions, component props, or template strings' is generic review language until the formatting qualifier arrives, creating minor overlap risk with general code-review skills. This fits 'mostly distinct; minor overlap risk with closely related skills' rather than the minimal-conflict score-5 anchor.