Accessibility Prover MCP for AI. Validate your components before they are coded.
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Accessibility Prover validates component specifications against WCAG 2.2 AA standards before you write code. This MCP checks five critical areas: semantic HTML structure, keyboard focus traps, contrast ratios, screen reader readiness, and motion safety.
It acts as a pre-build gate, catching invisible barriers like div soup or inaccessible animations that automated linters miss.
What your AI can do
Validate accessibility
It validates if your UI design meets all WCAG 2.2 AA standards by checking semantic HTML, keyboard navigation, contrast ratios, screen reader context, and motion safety.
It checks if you used correct HTML elements (like <button> for actions) instead of relying on non-semantic tags like <div>.
You ensure every interactive element is reachable via the Tab key, and that modals properly trap focus so users don't get lost in the DOM.
It measures foreground/background color ratios across all states (default, hover, focus) to ensure they meet the minimum 4.5:1 standard.
The tool verifies that images have descriptive alt texts and that icon buttons include necessary aria-label attributes for assistive technology.
You confirm that all animations respect user preferences, specifically checking for the required @media (prefers-reduced-motion) overrides.
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Accessibility Prover: 1 Tool Available
This single tool lets you run structured checks on your UI components to validate semantic HTML, keyboard navigation, contrast ratios, and ARIA annotations before development begins.
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Start using Accessibility Prover on VinkiusValidate Accessibility
It validates if your UI design meets all WCAG 2.2 AA standards by checking semantic HTML, keyboard navigation, contrast ratios, screen...
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Works with Claude, ChatGPT, Cursor, and more
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This connection provides 1 powerful capabilities that interface natively with Claude, ChatGPT, Cursor, and other compatible AI platforms. No middleware. No custom integration required.
It’s a pain to keep track of every little detail.
Today, fixing accessibility often means multiple manual checks. You have to verify that every button uses a semantic `<button>` and not just a clickable `<div>`. Then you manually check the contrast ratio for default, hover, and focus states across dozens of color combinations. If you miss one label or forget to add the correct `aria-label` to an icon, the entire component fails.
With this MCP, you input the component's full specification once. It runs all those checks—semantic structure, contrast ratios, alt text, focus traps—and immediately gives a structured verdict. You get actionable fixes before it ever becomes code.
You Get Structured Compliance with validate_accessibility
The tedious process of coordinating between design color palettes, developer focus order, and legal compliance documentation disappears. The MCP consolidates all those rules into one structured input that passes through five distinct decision pivots.
What's different now is the shift from remediation to prevention. You build accessible components correctly the first time, every time.
What your AI can actually do with this
Writing UI components means thinking about more than just how they look. Accessibility Prover forces you to think about compliance from the start. Instead of waiting for a painful post-launch audit—or worse, facing legal fines under regulations like EAA 2025—you run this MCP early in the design process. It validates your component specifications against WCAG 2.2 AA standards using structured reasoning, not just by scanning raw HTML.
You connect it via Vinkius and use it as a proactive gate. This means your AI agent or front-end developer can't generate code until the tool confirms five key things: that you used proper semantic tags (like <button> instead of a clickable <div>), that keyboard users can reach every element, that color contrast passes 4.5:1, and that screen readers have all the necessary labels.
It’s about catching structural flaws before they even hit your repository.
019e599a-f27a-71df-a461-772595c49ff6 Here's how it actually works
The bottom line is you get an auditable, prioritized checklist that proves your component meets compliance requirements before a single line of production code is written.
Submit a structured specification of your component. This includes the raw HTML structure, color values with hex codes, and descriptions of keyboard behavior.
The MCP runs this data through five distinct decision pivots—semantic HTML, keyboard navigation, contrast ratio, screen reader context, and motion safety.
You receive one of six structured verdicts (e.g., A11Y_PROVEN or CONTRAST_FAILING) detailing exactly which WCAG standard failed and what the specific fix needs to be.
Who is this actually for?
Front-end engineers and design system architects who are tired of last-minute accessibility audits. It's for anyone building complex, reusable components that need to satisfy both usability standards and impending legal requirements like the EAA 2025.
They use this MCP in their component library's pre-commit hook to fail builds if a new element uses non-semantic HTML or lacks proper focus traps.
They run the tool against entire design system specifications to create an auditable compliance record for regulatory review.
They use it during early wireframing stages, feeding in color hex codes and interaction specs before handing off the component definition to code.
What Changes When You Connect
Catches structural flaws like 'div soup' and missing focus traps early. This prevents the most common agent failure mode—creating inaccessible, div-based layouts.
Reduces legal risk by creating auditable records for EAA 2025 compliance. You demonstrate due diligence with every component validation run.
Saves time and budget. Fixing a contrast ratio during design takes minutes; fixing it after production requires multiple sprints and legal review.
Goes beyond simple linting. It analyzes behavior, ensuring things like form-label associations and aria-label usage are correct, not just that the element exists.
Tests five dimensions simultaneously (semantic HTML, keyboard flow, contrast, screen reader, motion). The output is an actionable verdict, not a vague severity score.
See it in action
Pre-commit gate for component libraries
A team needs to merge 50 new components. Instead of manual testing, they run the MCP on every single one. If any component fails validate_accessibility due to a contrast failure or missing tab order, the build automatically blocks until the spec is fixed.
AI agent guardrail
An AI coding agent generates a new user profile widget. The MCP intercepts the generated specification and runs it through validate_accessibility. The agent receives a verdict of KEYBOARD_TRAPPED and an explicit fix: 'Add focus traps to this modal.' This prevents inaccessible code from being committed.
EU market launch compliance
Before launching in the EU, product managers run every user-facing component through the MCP. The structured records it generates provide immediate proof of due diligence for EAA 2025 audits, mitigating huge legal liabilities.
Auditing legacy codebases
The team wants to modernize an old feature set. They feed the existing component's HTML and behavior into validate_accessibility. The tool returns a prioritized backlog showing which components are blocking (DIV_SOUP) versus merely degraded (CONTRAST_FAILING).
The honest tradeoffs
Treating it like a runtime scanner
Pointing the MCP at a live production URL and expecting it to crawl pages or give results like Lighthouse/axe-core.
You must submit structured specifications—the component's HTML, color hex codes, and behavior details. Use this tool during design time; save a browser-based DOM scanner for test time.
Submitting vague visual descriptions
Sending 'The button is dark gray on white background with some text in it.' without technical data.
Always provide the specific dimensions: semantic HTML elements, hex color pairs (e.g., #4A5568 on #FFFFFF), and explicit ARIA attributes.
Checking only default views
Providing contrast values for a button's normal state but forgetting to include the hover, focus, or active states.
WCAG 2.2 AA requires compliance across all interactive states. Submit all five states (default, hover, focus, active, disabled) for every element.
When It Fits, When It Doesn't
Use this MCP if your requirement is pre-build validation of component specs—before you commit code and before the feature ships. Specifically, use it when: 1) AI agents are generating UI components, and you need an immediate guardrail against inaccessible output; 2) Your product targets EU markets and requires auditable EAA 2025 compliance evidence per component; or 3) You're building a design system and need to enforce semantic HTML usage. Don’t use it if: 1) You just need to scan a live, rendered page (use a browser-based DOM scanner); 2) You only have visual mockups without technical specifications (you must supply the structured input); or 3) You are looking for automated code fixes—the MCP diagnoses and tells you what's broken; it doesn't rewrite the code.
Questions you might have
Why does Accessibility Prover reject divs with click handlers? +
A has no native keyboard interactivity, no focusability, and no implicit ARIA role. Adding `onclick` creates a visual button that keyboard and screen reader users cannot operate. Native elements provide focus, Enter/Space activation, and the 'button' role automatically — no extra JavaScript required.
What is a focus trap and when is it required? +
A focus trap constrains Tab navigation inside a specific element — typically a modal, dialog, or dropdown — so users cannot navigate to the underlying page while the overlay is active. WCAG 2.4.3 (Focus Order) requires it for all modal dialogs. Without it, a keyboard user can Tab behind the modal into invisible content.
Does Accessibility Prover check contrast across all interactive states? +
Yes. The contrastCompliant pivot validates foreground/background color combinations across five states: default, hover, focus, active, and disabled. A button that passes contrast in its default state but fails on hover (e.g., light gray text on white) is flagged as CONTRAST_FAILING.
How is this different from axe-core or Lighthouse? +
axe-core and Lighthouse scan rendered HTML in a browser — they detect violations after the code is built and running. Accessibility Prover validates UI specifications before code is written. It reasons about component behavior, keyboard flows, and interaction states at the design level, catching architectural issues that post-build scanners cannot see because they only inspect the final DOM.
Can I use Accessibility Prover with an AI coding agent? +
Yes — that is a primary use case. AI coding agents default to div-based layouts because divs are syntactically simpler. Accessibility Prover acts as a guardrail: the agent submits its component specification, the prover validates it against 5 pivots, and the agent receives a structured verdict with specific fixes before writing code.
What does the European Accessibility Act (EAA 2025) mean for my product? +
Since June 2025, the EAA requires all digital products and services sold in the EU to meet accessibility standards equivalent to WCAG 2.1 AA (with WCAG 2.2 AA as the recommended benchmark). Non-compliance carries fines up to 5% of annual revenue and potential market withdrawal. Accessibility Prover helps demonstrate compliance as a build-time gate, creating an auditable validation record.
What input format does Accessibility Prover expect? +
Submit each component as structured text covering 5 dimensions: (1) Layout — the HTML elements and hierarchy, (2) Keyboard — tab order, focus indicators, focus traps, (3) Contrast — foreground and background hex values with computed ratio, (4) Screen Reader — alt texts, aria-labels, form-label associations, (5) Motion — animation properties and prefers-reduced-motion handling. The tool reasons about each dimension independently.
Does Accessibility Prover support WCAG 2.2 AAA? +
The tool validates against WCAG 2.2 AA, which is the legally required level under the EAA 2025 and the practical target for most products. AAA requirements (e.g., 7:1 contrast ratio, sign language interpretation) are not enforced — they are aspirational goals that few products achieve fully.
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