Conciseness

The body is mostly lean navigational tables, but the "Key Features" bullet list ("Vite-native: Uses Vite's transformation pipeline...", "Jest-compatible: Drop-in replacement for most Jest test suites") restates facts Claude already knows and duplicates the description, and the time-sensitive note "based on Vitest 5.1.0-beta.1, generated at 2026-10-23" is not placed in a deprecated/old-patterns section. Not 4 because these sections could clearly be trimmed; not 2 because the bulk of the body is efficient index content, not verbose explanation.

Actionability

The body contains no code or commands at all — every statement ("Built-in coverage via V8 or Istanbul", "Multi-threaded workers for parallel test execution") describes rather than instructs, and all executable guidance is deferred to references with only high-level pointers like "Mocking | Mock functions, modules, timers, dates with vi utilities". Not 3 because there is not even pseudocode or a minimal quick-start snippet in the body; not 1 because the topic-to-reference mapping is concrete and correct as a navigation index.

Workflow Clarity

This is a single-action index skill: find the topic in a categorized table (Core / Features / Advanced) and open the matching reference — the action is unambiguous, matching the rubric's simple-skill exception. There are no destructive or batch operations, so no validation cap applies. Anti-drift check: anchor 4's 'most checkpoints' language presumes a multi-step sequence that does not exist here, so the simple-skill 5 stands.

Progressive Disclosure

The body is a pure overview and every one of the 19 referenced files (references/core-config.md through advanced-projects.md) exists, is linked with topic + one-line description in clearly labeled tables, and is one level deep — spot checks show references contain substantive content and only cross-link to sibling files, not deferred content chains. This matches the anchor for a clear overview with well-signaled one-level-deep references.

Specificity

Quotes like "writing tests, mocking, configuring coverage, or working with test filtering and fixtures" name the domain plus several concrete actions. Not 5 because coverage has gaps (snapshots, assertions/matchers, environments, benchmarking are absent from the description); not 3 because it lists well more than 1-2 concrete actions.

Completeness

Explicitly answers both: what ("Vitest fast unit testing framework powered by Vite with Jest-compatible API") and when ("Use when writing tests, mocking, configuring coverage, or working with test filtering and fixtures") with concrete trigger phrases. Anti-drift check against anchor 4 confirms the 'when' clause is explicit and specific, not merely present.

Trigger Term Quality

Natural phrases users would say are present: "writing tests", "mocking", "configuring coverage", "test filtering", "fixtures", "unit testing", "Jest-compatible". Not 5 because common variations and extensions are missing (e.g., ".test/.spec files", "running tests", "snapshots", "spies"); not 3 because keyword coverage goes well beyond a couple of generic terms.

Distinctiveness Conflict Risk

Clear niche anchored by "Vitest", "Vite", and "Jest-compatible API" with minor overlap risk against generic testing or Jest skills. Not 5 because trigger phrases like "writing tests" and "mocking" are generic across test frameworks; not 3 because the framework-specific framing keeps it well distinguishable.