heuristic

A structured UI review based on Nielsen's 10 usability principles and six common design laws. It scores each area and can also walk through the interface from a selected user's perspective.

In plain words
What is it for?
Use it to critique navigation, forms, controls, feedback, charts, and user flows, with optional persona-based checks.
Why use it?
It turns usability problems into specific, scored findings instead of a general opinion about whether a screen feels good to use.

Command

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add commands/educlopez/ui-craft/heuristic
Clone the repo
git clone --depth 1 https://github.com/educlopez/ui-craft
Per session 53 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 954 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00053 $0.00954
Opus 5 $0.00026 $0.00477
Sonnet 5 $0.00011 $0.00191
Haiku 4.5 $0.00005 $0.00095

Measured 3d ago against content hash c4f3963d16a7, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

heuristic scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

cli/assets/claude/commands/heuristic.md · 47 lines

What it actually says

Score the UI at $ARGUMENTS against Nielsen's 10 + 6 design laws. Load the ui-craft skill.

Step 1 — Load the methodology. Read references/heuristics.md for the full rubric, scoring definitions, design law details, and the required output format. Do NOT invent a new format or a new scale.

Step 2 — Walk Nielsen's 10 heuristics. Score each 1-5 per the rubric:

  • 1 blocks users · 2 severe friction · 3 works but confusing · 4 works, minor polish · 5 best-in-class

For every heuristic, write a concrete finding — quote text, count elements, name the broken flow. Vague findings are rejected.

Step 3 — Audit the 6 design laws. PASS / FAIL each with a specific detail:

  • Fitts's Law — touch target sizing, CTA placement
  • Hick's Law — choice density, nav + select sizing
  • Doherty Threshold — perceived latency, optimistic UI
  • Cleveland-McGill — chart encoding choice
  • Miller's Law — nav depth, form section counts
  • Tesler's Law — where complexity lives

Step 4 — Persona walkthrough (if --persona= present). If the args include --persona=<name>, load references/personas.md and run the matching walkthrough checklist. Supported: priya, jordan, adaeze, kwame, margo, all. Output the walkthrough as a | Checklist item | Pass/Fail | Finding | Impact | table. Without the flag, skip this step.

Step 5 — Rank findings by impact tag. Impact order: blocks-conversion > adds-friction > reduces-trust > minor-polish. Include at most 5 findings in the ranked list; cut anything at minor-polish unless there are no higher-impact findings.

Step 6 — Compute the UsabilityScore. Roll the scorecard into a 0-100 number + grade per the UsabilityScore formula in references/heuristics.md: heuristic_base = round(((mean(nielsen_scores) − 1) / 4) × 100), minus 5 × (failed design laws), clamped [0,100]. Same A/B/C/D/F bands as UICraftScore. Always label it (judged) — it is not deterministic and must never gate CI. If the args include --json, also emit the machine-readable block. If the user asks for the full picture, build the Extended quality report by fetching the deterministic UICraftScore (node scripts/eval.mjs <path> --json or the score_ui MCP tool) and placing both side by side — never average them.

Step 7 — Output. Use the exact scorecard format in references/heuristics.md:

  1. ## Heuristic Scorecard table
  2. ## Design Law Audit table
  3. ## Persona Walkthrough table (only if --persona= was passed)
  4. ## Top findings (ranked by impact) — numbered list, 3-5 items
  5. ## UsabilityScore block — the 0-100 score + grade + component breakdown

Knob awareness: knob-agnostic. Usability is not a knob — a 2 is a 2 whether CRAFT_LEVEL is 3 or 9. Do not soften scores based on CRAFT_LEVEL.

Output contract:

  • This command produces a critique artifact, not code. No edits unless the user explicitly asks in a follow-up.
  • The scorecard is machine-parseable markdown. A PM can paste it into any issue tracker and file tickets row-by-row. Frame it that way in any preamble.
  • No "First Impressions" paragraph, no hedging, no praise padding. Tables + ranked list only.

Do NOT edit code. This is a scored critique.

Next step: Fix the findings, then /finalize — the scorecard is the input to a gated ship (rung 3).

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 47 lines · 53 tokens per session scan A c4f3963d16a7

Subscribe to this mod's changes

heuristic is a command published in the GitHub repository educlopez/ui-craft (298 stars, last pushed 14d ago), licensed MIT. It adds 53 tokens to every session and 954 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.