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Reference-grade guide to the canonical usability principles — Nielsen's 10 heuristics, Norman's design fundamentals, Shneiderman's 8 golden rules, Rams' 10 principles — plus how to run a heuristic evaluation across any web, mobile, desktop, TV, or voice screen.
Passed 21 of 22 test cases with the skill, and 19 of 22 without it.
3 fixed18 passed either way0 still failing1 broke
Tokens, turns and time describe resource use, not a dollar price.
One of 3 test cases the skill fixed. Same model, same prompt, with and without the skill.
I need a heuristic usability evaluation for our app's multi-step checkout workflow. Here is the flow description: step 1 has a standard form with address inputs, step 2 requires entering payment details but the button doesn't disable after tapping, and errors show server trace logs like raw database exceptions. Please inspect this flow against standard user interface heuristics and deliver a structured audit log formatted as a table containing the location, specific principle breached, problem explanation, priority rating, and recommended solution.
| Checked | Without skill | With skill |
|---|---|---|
| The evaluation uses Nielsen's numeric 0 to 4 severity scale. | Missed | Passed |
| The review identifies raw database error trace output as an error handling heuristic violation. | Passed | Passed |
The instructions your model reads when the skill loads.
The durable, attributed laws of usable interfaces. These are not opinions — they are field-tested principles from Jakob Nielsen, Don Norman, Ben Shneiderman, and Dieter Rams. Use this skill to design screens that don't need explaining, and to evaluate any UI (web, mobile, desktop, TV, voice) against a shared, defensible standard.
How to use: design against the heuristics; evaluate with the method in §5. When you flag a problem, name the heuristic it violates and rate its severity — that turns a subjective "I don't like this" into a prioritized, fixable finding.
Published by Jakob Nielsen in 1994 (refined from a 1990 factor analysis with Rolf Molich), now maintained by Nielsen Norman Group (NN/g). They are "heuristics" — broad rules of thumb, not narrow guidelines — because they apply across every interface ever built. Memorize them.
Principle. The system should always keep users informed about what is going on, through appropriate feedback within reasonable time. Why it matters. Reduces uncertainty. Users build trust when the system communicates; they abandon and double-click when it goes silent. Follows it. A file-upload bar showing "3 of 8 files · 1.2 MB/s · ~12s left." A "Saved" indicator the instant autosave fires. A map app pulsing while it acquires GPS. A button that swaps to a spinner + "Submitting…" on tap. Violation. Tap "Pay" → the screen freezes with no spinner, no disabled state. The user taps again and gets charged twice. Fix. Disable the button on first tap, swap the label to a loading state, and confirm completion ("Payment received") or failure explicitly.
Principle. Speak the users' language — words, phrases, and concepts familiar to them — and follow real-world conventions, making information appear in a natural, logical order.
Why it matters. Jargon forces translation; users misread, mistrust, or quit.
Follows it. A trash/recycle bin for deletion. "Cart" and "Checkout" in commerce. A thermostat that shows degrees, not sensor codes. A calendar reading "Tomorrow, 2 PM" not "2026-06-06T14:00Z."
Violation. An error reads EACCES: permission denied, open '/var/db'. A medical app labels a field "Episode of care encounter ID."
Fix. Translate to the user's domain: "We couldn't save your file — you don't have permission to write here." Use the words your actual users use (test with five of them).
Principle. Users often choose functions by mistake and need a clearly marked "emergency exit" to leave the unwanted state — support undo and redo. Why it matters. Freedom to reverse encourages exploration; its absence breeds fear. Follows it. Gmail's "Undo Send." Photoshop's history/undo stack. A "Cancel" on every modal. A discardable draft. The browser back button always restoring state. Violation. A multi-step wizard with no Back button. "Are you sure?" with only an OK. A bulk "Archive all" with no undo. Fix. Add Cancel/Back/Close to every flow. Prefer undo (reversible after the fact) over nagging confirmations; offer a 5–10s "Undo" toast for bulk and destructive actions.
Principle. Users shouldn't wonder whether different words, situations, or actions mean the same thing. Follow platform and industry conventions. (Per Nielsen's "Jakob's Law": users spend most of their time on other sites, so they expect yours to behave like those.) Why it matters. Consistency lets learning transfer; inconsistency forces relearning. Follows it. Primary action always the same color/position. iOS apps using the native share sheet. One icon meaning one thing everywhere. Hamburger menu top-left, account top-right. Violation. "Submit" on one screen, "Send" on the next, "Go" on a third — all the same action. A custom dropdown that ignores keyboard arrow-key conventions. Fix. Build and enforce a design system / component library. Adopt platform HIG (Apple), Material (Android), or your in-house standard. Audit terminology for one word per concept.
test cases passed, vs 19 / 22 without
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