Conciseness

The ~45-line body is lean and assumes Claude's competence: no explanation of what CSS or design systems are, just project-specific facts — source-of-truth file paths, a decision order, a literal-vs-token table, and four non-obvious gotchas. Every token earns its place, matching the 5 anchor; the 4 anchor would require trimmable over-explanation, and none is present.

Actionability

Guidance is directly executable: exact paths ("node_modules/@rolemodel/optics/dist/tokens/tokens.json", "app/assets/stylesheets/components/optics-overrides/{component}.css"), a concrete instead-of/use table with real token names, and specific verification commands (check names against tokens.json, check both values in scale_color_tokens.css). The common cases (picking a token, overriding a component, theming) are all covered specifically.

Workflow Clarity

The "Before writing CSS" section is a clear 3-step decision sequence, and validation checkpoints are explicit throughout: "Check dist/css/components/", "Check the name against tokens.json" (for the silent-failure gotcha), "check both values in scale_color_tokens.css" for dark mode, and "read references/theming.md before changing any --op-color-* value". Each failure mode named in Gotchas comes with an explicit check, which fits the 5 anchor's explicit validation steps.

Progressive Disclosure

The body is a well-organized overview and the theming detail is split at exactly the right boundary into references/theming.md (verified to exist, self-contained, one level deep), signaled twice with clear context ("See references/theming.md before changing any --op-color-* value"). Structure matches the 5 anchor: clear overview, well-signaled one-level-deep references, easy navigation.

Specificity

Lists multiple concrete actions in third person — "Styles Rails views", "picking a color, spacing, font, radius, or shadow value", "fixing hard-coded CSS values", "adding a project token", "theming an app (brand colors, fonts, color scales, dark mode)" — with comprehensive coverage of both styling and theming tasks. It clearly exceeds the 4 anchor ("several specific actions; minor gaps") since no common task in the domain is left out.

Completeness

First sentence answers "what" (styles Rails views with Optics components, tokens, and theme overrides), and an explicit "Use when..." clause enumerates concrete "when" triggers, reinforced by a second sentence of quoted user phrasings. Both what and when are explicit with concrete triggers, exactly the 5 anchor; the 4 anchor requires a weaker or less specific "when".

Trigger Term Quality

Combines natural colloquial phrases users would actually say ("style this", "make this look like the design", "fix the hard-coded colors", "change the brand color", "add dark mode") with technical triggers ("css", "design tokens", "--op-", "color scale", "dark mode"). Coverage includes synonyms at both the lay and technical level, matching the 5 anchor rather than leaving a few natural terms missing.

Distinctiveness Conflict Risk

The niche is clear (RoleModel's Optics design system for Rails views, with a named package), but the broad trigger "Use when writing or reviewing CSS" overlaps with closely related styling skills in the same ecosystem (e.g., the bem-structure skill referenced in the body). Minor overlap risk with a closely related skill fits the 4 anchor; it does not reach 5's "minimal conflict risk" because generic CSS-writing triggers would fire for adjacent skills.