nielsen-heuristics

nielsen-heuristics is a skill for Claude Code, Codex from glebis/humane-agentic-design. It costs 118 tokens per session (2,270 once invoked), scanned A, original, MIT.

A formal checklist for reviewing an interface against Jakob Nielsen's 10 usability principles, such as clear system feedback and easy error recovery.

In plain words
What is it for?
Use it to evaluate screenshots, live websites, HTML, code, interface descriptions, or product specifications for usability issues.
Why use it?
It replaces an informal design critique with consistent findings, evidence from the supplied artifact, and a severity rating for each problem.

Skill for Claude CodeCodex

Written for Claude Code and Codex: shipped in a Claude Code plugin, but also agents/openai.yaml present.

Part of the humane plugin — 21 skills, 1 agent shipped together

Good fit Use it to evaluate screenshots, live websites, HTML, code, interface descriptions, or product specifications for usability issues.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/glebis/humane-agentic-design/nielsen-heuristics
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.

Any agent
npx skills add glebis/humane-agentic-design --skill nielsen-heuristics
Clone the repo
git clone --depth 1 https://github.com/glebis/humane-agentic-design

Made for: Claude Code, Codex.

Or install humane, the plugin that ships this one along with the rest of its 21 skills, 1 agent.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for nielsen-heuristics

README.md
[![agentmods](https://agentmods.dev/badge/skills/glebis/humane-agentic-design/nielsen-heuristics/github.svg)](https://agentmods.dev/skills/glebis/humane-agentic-design/nielsen-heuristics)
Your own site
<a href="https://agentmods.dev/skills/glebis/humane-agentic-design/nielsen-heuristics"><img src="https://agentmods.dev/badge/skills/glebis/humane-agentic-design/nielsen-heuristics/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for nielsen-heuristics

Your own site · 80×15
<a href="https://agentmods.dev/skills/glebis/humane-agentic-design/nielsen-heuristics"><img src="https://agentmods.dev/badge/skills/glebis/humane-agentic-design/nielsen-heuristics.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 118 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,270 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 5.1 $0.00118 $0.02270
Opus 5 $0.00059 $0.01135
Sonnet 5 $0.00024 $0.00454
Haiku 4.5 $0.00012 $0.00227

Measured 11d ago against content hash 71d2e9a91795, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

nielsen-heuristics 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 11d 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.

humane/skills/nielsen-heuristics/SKILL.md · 120 lines

How it starts

The opening of the file, as written. The whole thing — 120 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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.

Announce at start: "I'm using the humane:nielsen-heuristics skill to evaluate this against Nielsen's 10 usability heuristics."

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 humane:review, which orchestrates this skill alongside layout-rules, ux-writing, walkthrough, and design-tokens contrast — and marks the domains it cannot cover rather than improvising them. For post-build polish specifically, impeccable:audit is the right tool if installed.

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 to observe states and flows, following walkthrough's references/driven.md for the tool ladder, device matrix, and screenshot evidence contract (that file is the single owner of the driving procedure). A heuristic only observable on a tier that was not driven is N/A at that tier, not silently assessed from desktop.
  • Codebase / HTML page — grep and read the UI source.

Read the full file on GitHub · 120 lines

Files

What ships with it

7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 11d ago First seen · 120 lines · 118 tokens per session scan A 71d2e9a91795

Subscribe to this mod's changes

nielsen-heuristics is a skill published in the GitHub repository glebis/humane-agentic-design (28 stars, last pushed today), licensed MIT. It adds 118 tokens to every session and 2,270 once invoked, about $0.0006 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.

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