Conciseness

The ~45-line body is efficient and assumes TypeScript competence, but has minor redundancy: the first Quick Reference bullet ('array[0] is typed as T even if the array is empty') restates the intro paragraph, and the closing 'Rule page' URL duplicates the frontmatter url. Matches 'efficient; minor instances of over-explanation that could be trimmed'; not a 5 because of that duplicated content.

Actionability

Concrete, specific instruction guidance: 'Check whether noUncheckedIndexedAccess is enabled in the project's tsconfig.json', 'scan for array index accesses (arr[0], arr[i])', 'enable... then update any array index accesses that TypeScript now flags'. Per the instruction-skill scoring note the absent code is acceptable since the concrete examples are delegated to references/rule.md; minor gaps (no explicit tsc command in the body) keep it from 5.

Workflow Clarity

The Check → Fix → Explain → Code Review sequence is clear, but validation checkpoints are implicit only — there is no step to run tsc after enabling the flag, verify the build passes, or confirm all flagged accesses were updated. This matches 'steps listed but validation gaps; checkpoints missing or implicit'; not 4 because no checkpoint is ever made explicit.

Progressive Disclosure

A well-organized, under-50-line overview with a clearly signaled, one-level-deep pointer ('For full implementation details, code examples, and framework-specific guidance, see references/rule.md'), and the referenced file exists and contains exactly that material. Matches the clear-overview anchor, including the under-50-lines exception.

Specificity

Names the domain concretely ('auditing tsconfig.json for missing safety flags', 'array index access', 'runtime undefined errors') but never states what the skill actually does (enable noUncheckedIndexedAccess, fix flagged accesses). It lists usage scenarios rather than capabilities, matching 'names domain and 1-2 concrete actions, but not comprehensive'; not a 4 because the skill's own actions are absent.

Completeness

Only a 'when' is present — three trigger scenarios — with no statement of what the skill does. This matches the anchor 'only when is present without what' ('Use when working with documents'). It is not a 3 because there is no clear 'what' anywhere in the description, and the concrete-what phrasing only appears in the body, not the description.

Trigger Term Quality

Good natural keyword coverage: 'tsconfig.json', 'array index access', 'runtime undefined errors', 'TypeScript did not catch'. Missing common synonyms a user might say such as 'out of bounds', 'arr[0] is undefined', or 'optional chaining', so it falls short of the comprehensive-synonyms anchor at 5 but clearly above the midpoint.

Distinctiveness Conflict Risk

The combination of array index access, runtime undefined errors, and tsconfig safety-flag auditing carves a fairly distinct niche with low conflict risk. Minor overlap remains with general TypeScript strict-mode or linting audit skills because 'missing safety flags' is broad, keeping it below the clear-niche anchor at 5.