Web Quality Skills is a collection of agent skills for measuring and improving website performance, accessibility, search optimization, and browser usability. Developers use it with any web framework to run Lighthouse and Chrome DevTools checks, analyze Core Web Vitals and CrUX data, and apply WCAG and SEO guidance. The catalogue entries are the project's own skills, instructions, and plugin for agent-assisted web-quality work.
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.
npx skills add addyosmani/web-quality-skills --skill accessibilitygit clone --depth 1 https://github.com/addyosmani/web-quality-skillsWrote 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.
[](https://agentmods.dev/skills/addyosmani/web-quality-skills/accessibility)<a href="https://agentmods.dev/skills/addyosmani/web-quality-skills/accessibility"><img src="https://agentmods.dev/badge/skills/addyosmani/web-quality-skills/accessibility/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.
<a href="https://agentmods.dev/skills/addyosmani/web-quality-skills/accessibility"><img src="https://agentmods.dev/badge/skills/addyosmani/web-quality-skills/accessibility.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector warn
SkillSpector: 3 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Prompt Injection · line 50 Hidden instructions were detected in comments or invisible text. These could contain malicious directives. Manual review is recommended.Fix: Audit all comments and invisible characters. Remove any instructions that direct the agent to perform unauthorized actions. Use plain, reviewable content.
- high Prompt Injection · line 312 Hidden instructions were detected in comments or invisible text. These could contain malicious directives. Manual review is recommended.Fix: Audit all comments and invisible characters. Remove any instructions that direct the agent to perform unauthorized actions. Use plain, reviewable content.
- medium MCP Rug Pull · line 413 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00051 | $0.03619 |
| Opus 5.5 | $0.00020 | $0.01448 |
| Sonnet 5.5 | $0.00010 | $0.00724 |
| Haiku 4.5 | $0.00005 | $0.00362 |
Grade A, and why
accessibility 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 1mo 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.
Copies of this mod
8 near-identical copies found in the catalogue:
- accessibility — 100% identical, 0 lines differ
- accessibility — 89% identical, 16 lines differ
- accessibility — 89% identical, 16 lines differ
- accessibility — 89% identical, 0 lines differ
- accessibility — 86% identical, 44 lines differ
- accessibility — 86% identical, 150 lines differ
- accessibility — 86% identical, 44 lines differ
- accessibility — 84% identical, 20 lines differ
How it starts
The opening of the file, as written. The whole thing — 465 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Accessibility (a11y)
Comprehensive accessibility guidelines based on WCAG 2.2 and Lighthouse accessibility audits. Goal: make content usable by everyone, including people with disabilities.
Evidence-led audit workflow
When a rendered page is available:
- Run a live Lighthouse Accessibility audit when that capability is available; with Chrome DevTools MCP, use
lighthouse_audit. Use mobile navigation mode for a general public page or snapshot mode when reloading would lose authenticated or user-created state. - Use failed audit nodes to localize the relevant component or template instead of searching the whole repository for generic patterns.
- Inspect a rendered accessibility-tree snapshot for names, roles, states, landmarks, and heading structure; with Chrome DevTools MCP, use
take_snapshot. Exercise the affected flow with the keyboard. - Fix the source, then re-run the same audit and manual interaction.
If the live tools are unavailable, use Lighthouse CLI or axe for automated coverage and complete the same manual checks. Automated tools detect only a subset of accessibility barriers: a score of 100 is not WCAG conformance, and a low score does not replace issue-level evidence.
WCAG Principles: POUR
| Principle | Description |
|---|---|
| Perceivable | Content can be perceived through different senses |
| Operable | Interface can be operated by all users |
| Understandable | Content and interface are understandable |
| Robust | Content works with assistive technologies |
Conformance levels
| Level | Requirement | Target |
|---|---|---|
| A | Minimum accessibility | Must pass |
| AA | Standard compliance | Should pass (legal requirement in many jurisdictions) |
| AAA | Enhanced accessibility | Nice to have |
Perceivable
Text alternatives (1.1)
Images require alt text:
<!-- ❌ Missing alt -->
<img src="chart.png">
<!-- ✅ Descriptive alt -->
<img src="chart.png" alt="Bar chart showing 40% increase in Q3 sales">
<!-- ✅ Decorative image (empty alt) -->
<img src="decorative-border.png" alt="" role="presentation">
<!-- ✅ Complex image with longer description -->
<figure>
<img src="infographic.png" alt="2024 market trends infographic"
aria-describedby="infographic-desc">
<figcaption id="infographic-desc">
<!-- Detailed description -->
</figcaption>
</figure>
What ships with it
2 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.
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.
- 1mo ago First seen · 465 lines · 51 tokens per session scan A 267fb2a0707d
accessibility is a skill published in the GitHub repository addyosmani/web-quality-skills (2,985 stars, last pushed 2mo ago), licensed MIT. It adds 51 tokens to every session and 3,619 once invoked, about $0.0002 per session on Opus 5.5. 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.
Other skills, from other repositories
design-component
Design a UI component spec to the house quality bar — anatomy, variants, sizes, the 8 states, token mapping, and accessibility. Use when the user wants to design or document a component (button, input, tabs, toast, combobox, date picker, modal, etc.) at the spec level before or alongside code. For generating framework…
design-screen
Design or build a page, screen, landing page, website, app or UI from a request - the whole job, end to end. Use this for "design a landing page", "build a settings screen", "make me a website", "design the onboarding", "ออกแบบหน้าเว็บ", "ทำหน้า landing", "ออกแบบ UI", "ทำแอป". It runs the pipeline no single skill…
critique
Adversarial design critique of the current work — render it, look at it, and argue for rejection. Run after the gates are green, never instead of them.
scaffold-project
Scaffold a new design-product project that matches the recommended Claude Code layout (the reference structure). Use when starting a fresh product/app that will be built with this design system.
design-code
Generate production-ready, accessible, token-driven component code for ANY framework — React+Tailwind, Next.js, SwiftUI, Vue, Svelte, Angular, Solid, Web Components/Lit, React Native, Flutter, Jetpack Compose, vanilla CSS, or CSS-in-JS. Use when the user wants working UI code for a component or screen in a specific…
image-to-code
Turn a reference image, screenshot, or mockup into token-driven, accessible code — infer the design system from the reference (palette, type scale, spacing, radius, layout archetype), map it to the 3-tier tokens, rebuild it, then verify with the kit's gates. Use when the user provides a design/screenshot and wants…