Conciseness

The body is lean and assumes competence — it never explains what Vue, Webpack, or Mermaid are, and every line carries non-obvious domain decisions (e.g. 'smooth-streaming="auto" is the default and activates when typewriter=true or max-live-nodes <= 0'). Not a 5 because the opening line 'Use this skill when the host app is Vue 2 on Vue CLI or another Webpack 4-style stack' duplicates the frontmatter description, and a few glosses ('gives a polished entry animation') could be trimmed.

Actionability

Guidance is largely concrete: named functions ('createKaTeXWorkerFromCDN(...)', 'createMermaidWorkerFromCDN(...)'), an import path ('markstream-vue2/dist/index.css'), and ready prop/value pairs for each scenario ('smooth-streaming="auto", :fade="false", typewriter=true'). Not a 5 because there is no install command, no copy-paste import statement or code block, and the worker functions are given as ellipsis signatures rather than complete calls with arguments.

Workflow Clarity

A clear six-step sequence runs from environment confirmation through install, CSS import, worker strategy, renderer choice, to 'Validate with the smallest useful local dev or build command'. Not a 5 because step 6 is a directive to validate without naming an actual command, and there is no error-recovery loop if validation fails; not a 3 because a validation checkpoint is explicitly the final step and the ordering is unambiguous.

Progressive Disclosure

The skill is under 50 lines with no bundle files, and is organized into three well-labeled sections (Workflow, Default Decisions, Useful Doc Targets) with the doc targets serving as clearly signaled one-level navigation. Per the simple-skill guideline, well-organized sections alone warrant a 5 here; nothing is inlined that belongs in a separate file.

Specificity

The opening 'Integrate markstream-vue2 into a Vue 2 Vue CLI or Webpack 4 app' names the domain and target, and the when-clause enumerates concrete specifics ('CDN worker fallbacks for Mermaid or KaTeX', 'dist/index.css imports', 'Vue 2 composition-api shims', 'code block choices limited to stream-diffs or plain <pre>'). It falls just short of the 5 anchor because the 'what' rests on a single generic action ('Integrate') with the remaining specifics framed as trigger conditions rather than distinct capabilities.

Completeness

Both halves are explicit: 'Integrate markstream-vue2 into a Vue 2 Vue CLI or Webpack 4 app' answers what it does, and 'Use when Codex needs Webpack 4-friendly setup, CDN worker fallbacks...' answers when with concrete trigger phrases. This matches the 5 anchor ('clearly and explicitly answers both what AND when with concrete trigger phrases'); it is not a 4 because the when-clause is fully explicit rather than merely present.

Trigger Term Quality

Strong natural terms users of this stack would actually say: 'Vue 2', 'Vue CLI', 'Webpack 4', 'Mermaid', 'KaTeX', 'composition-api'. Not a 5 because it lacks synonyms and file-extension variants (e.g. .vue, webpack.config.js, vue.config.js) that would broaden natural recall, and 'markstream-vue2' itself is the only package-name spelling offered.

Distinctiveness Conflict Risk

It carves out a clear niche — one named library pinned to a specific stack (Vue 2 + Vue CLI/Webpack 4) with distinctive tokens (markstream-vue2, stream-diffs, dist/index.css) — so it would rarely fire for a different skill. Not a 4 because the overlap risk with a generic Vue or Webpack skill is negligible given the package-name triggers.