Nielsen Heuristics Skill for Claude

Nielsen Heuristics Validator

> Mascot: assets/jakob-nielsen.png — a line-art portrait of Jakob Nielsen. Surface it (embed or attach) when producing a rendered/HTML report or a shareable summary, as the evaluation's signature. It is an output asset, not context to read while evaluating.

Run a rigorous, evidence-disciplined heuristic evaluation against Jakob Nielsen's 10 usability heuristics (Nielsen & Molich 1990, refined 1994). The value over an ad-hoc "critique this UI" prompt is a consistent rubric plus honesty guards: sharp per-heuristic probes, a per-finding severity scale, a mandatory evidence-locator requirement, and correct handling of artifacts that have no observable interface.

Scope guard (read first)

This skill does ONE thing: a formal heuristic inspection. It does NOT run a parallel accessibility (WCAG) audit, performance audit, or general design critique. Flag an accessibility issue only when it is also a heuristic violation (e.g., an invisible focus state violates H1: visibility of system status). If the user wants comprehensive multi-dimension auditing, defer to the impeccable:audit skill instead.

Step 1 — Detect artifact type and select a mode

Heuristic evaluation is an inspection of an *interface*. Some inputs have one to observe; some only describe one that does not yet exist. Detect the input type, then announce the mode and why.

Evaluation mode (observable interface → findings are severity-scored):

• Screenshot / image — read it visually.
• Live URL — drive it with browser tools to observe states and flows.
• Codebase / HTML page — grep and read the UI source.

Design-risk review mode (interface described but not built → findings are UNSCORED risk flags):

• Interface description (text/markdown).
• JTBD / spec document.

Never assign a 0–4 severity to a pure spec or JTBD doc — there is no running system to observe, so a number would be speculation dressed as measurement. Reframe the question as *"which heuristics does this design direction put at risk when built."*

See references/artifact-guide.md for how to ingest each type, which heuristics are assessable vs. N/A for it, and which mode applies.

Step 2 — Inventory (mandatory, before judging)

Enumerate the concrete units that will be examined BEFORE forming any finding. This is the structural safeguard against shallow, agreeable output.

• Evaluation mode: list the screens, key elements, and flows observed.
• Design-risk mode: list the spec sections / described flows.

Walk this inventory in Step 3. Do not evaluate from vibes.

Step 3 — Walk all 10 heuristics

Load references/heuristics.md for the definition, "what to look for" probes, common violations, and the 0–4 severity rubric. For EACH of the 10 heuristics:

• Produce zero or more findings (not exactly one — real evaluations have zero for some heuristics and several for others).
• Every finding MUST cite an evidence locator. Unevidenced findings are disallowed. A locator is one of: a described screenshot region, a DOM element/CSS selector, a file:line reference, a quoted sentence from the spec, or the specific URL interaction performed.
• In evaluation mode, assign a severity 0–4 per finding. In design-risk mode, mark each as an unscored risk flag ("potential, unverified").
• If a heuristic is not assessable from this artifact (e.g., undo/redo on a static screenshot), mark it N/A and state why.
• If a heuristic has no findings, state what was checked ("checked X, Y, Z — no issues") — never silently bless it.

Step 4 — Emit the report (choose an output format)

Findings are always grouped by heuristic with a max-severity rollup, followed by Top-3 prioritized fixes and the Verdict. Two render targets:

• markdown (default) — emit inline using references/report-template.md. Use this unless the user asks for a rendered/shareable report.
• tufte — a Tufte-style standalone HTML report. Follow references/tufte-preset.md: build the structured findings first, then invoke the tufte-report skill with that preset (which maps findings onto its strip-chart / status-strip / flyout blocks and uses assets/jakob-nielsen.png as the hero). Trigger when the user says "tufte report", "HTML report", "shareable report", or "make it pretty".

Select the format from the user's request; if ambiguous and they only said "report", default to markdown.

Verdict (scoped — never "ready to ship")

A single evaluator finds only ~1/3 of usability problems (Nielsen); 3–5 evaluators are recommended for confidence. The verdict must carry this caveat and use these defined levels (evaluation mode):

• Blockers present — one or more severity-4 findings.
• Major issues — one or more severity-3, none at 4.
• Minor issues only — nothing above severity-2.
• No blockers found in heuristic inspection — clean pass, with the explicit single-evaluator caveat.

Design-risk mode produces a risk summary (which heuristics are most at risk, and what to specify to de-risk them) instead of a scored verdict — there are no severities to roll up.

Step 5 — Export findings as tasks (optional)

When the user asks to "create tasks", "file these", "make Linear issues", "open beads", etc., turn qualifying findings into tracker issues. Follow references/task-export.md for the exact command templates and field mapping.

Rules (all defaults overridable per run):

• Threshold: default severity ≥ 3 (Major + Catastrophe). The user may set another (≥ 4, ≥ 2). In design-risk mode there are no severities — only export flags the user explicitly selects or the "highest-risk" flags named in the risk summary, and say so.
• Propose, then confirm (mandatory gate): first print the list of tasks that WOULD be created — title, severity, target tracker, and the heuristic — and ask for confirmation. Create nothing until the user approves. This gate is required for Linear (outward-facing/cloud); keep it for Beads too.
• Target: Linear (linear CLI, cloud) or Beads (bd CLI, local/per-repo). Ask which if unspecified. Beads requires being inside the target repo (its .beads dir); confirm the repo before creating.
• One task per finding, titled [H<n>] <short finding>, with the evidence locator, fix, and severity in the body. Map severity → tracker priority per references/task-export.md.
• After creation, report back the created issue IDs/URLs.