Conciseness

The ~45-line body is efficient and assumes Claude's competence — no explanation of what WCAG or epilepsy is beyond the one safety-framing sentence. It falls short of anchor 5 only through minor redundancy: the 'Check' section ('Verify no content flashes more than 3 times per second, and that any flashing content occupies less than 25% of the viewport') restates the first two Quick Reference bullets almost verbatim, and the intro sentence's 3-60 Hz fact is repeated in 'Explain'.

Actionability

'Test animated GIFs, videos, and CSS animations for rapid flashing patterns' and 'Replace flashing effects with fade transitions or static alternatives' are concrete directions, but 'Use animation tools to measure flash frequency' names no actual tool or method (e.g., PEAT, browser animation/devtools inspection, reading the animation duration), and the body contains no executable example — the CSS examples live only in references/rule.md. This matches anchor 3: some concrete guidance but incomplete, with key measurement details missing; anchor 4 would require the specific verification method to be named.

Workflow Clarity

The Check → Fix → Explain → Code Review sections form a clear, sensibly ordered sequence for a simple single-purpose skill, and 'note how to verify the fix with browser accessibility tooling' signals a validation checkpoint. It is not anchor 5 because verification is only gestured at — there is no explicit re-measure/re-check step after applying a fix — leaving a minor validation gap consistent with anchor 4.

Progressive Disclosure

The body is a concise overview with well-organized sections and a single, clearly signaled one-level-deep pointer: 'For full implementation details, code examples, and framework-specific guidance, see references/rule.md' — and references/rule.md does exist (203 lines) with no further nesting. This matches anchor 5: clear overview, appropriately split content, easy navigation.

Specificity

The description names the domain ('Prevent seizure-triggering flashing content') and lists concrete actions ('Check native semantics first, then inspect keyboard behavior, focus flow, accessible names, and screen-reader output'), but those actions are generic accessibility-review boilerplate rather than the skill's actual flashing-specific capabilities (measuring flash frequency, checking the 25% viewport threshold). It matches anchor 3 — domain plus 1-2 concrete actions, not comprehensive — and falls short of anchor 4 because the listed actions don't cover what the skill actually does.

Completeness

Both parts are present: an explicit 'Use when reviewing rendered HTML, interactive components, or design-system patterns...' trigger clause, and a 'what' expressed through the check/inspect actions. It is not a 5 because the 'what' describes generic review activity rather than concretely stating the skill verifies and fixes flashing content against WCAG 2.3.1 thresholds; it exceeds anchor 3 because the 'when' is explicit, not merely implied.

Trigger Term Quality

It contains relevant natural terms ('flashing content', 'seizure', 'rendered HTML'), but misses common variations a user would plausibly say: 'animation', 'GIF', 'video', 'strobe', 'flicker', 'photosensitive epilepsy', or 'WCAG'. Anchor 3 ('some relevant keywords but missing common variations or synonyms') fits; anchor 4 would require broader coverage of these synonyms.

Distinctiveness Conflict Risk

'Prevent seizure-triggering flashing content' names a clear niche, but the trigger clause ('reviewing rendered HTML, interactive components, or design-system patterns') plus generic keyboard/focus/screen-reader checks overlaps heavily with any general accessibility-review skill, so it could fire for the wrong skill. This is anchor 3 — somewhat specific but overlap risk remains; not anchor 4 because the generic a11y phrasing creates real conflict risk with sibling accessibility rules.