A11y Tools MCP Server

mcp-a11y-tools

Web accessibility analysis tools for AI agents, served over the Model Context Protocol (MCP).

Tools

check_alt_text

Analyze images in HTML for missing, empty, or low-quality alt text.

• Detects missing alt attributes
• Identifies decorative images (alt="" with role="presentation")
• Flags low-quality alt text (e.g., "image", "photo", filenames)
• Checks linked images, <input type="image">, and <area> elements

check_heading_hierarchy

Validate heading structure for proper nesting and content quality.

• Verifies h1-h6 order with no skipped levels
• Ensures a single <h1> per page
• Detects empty, too-short, or too-long headings
• Supports role="heading" with aria-level
• Returns a visual tree of the heading outline

check_color_contrast

Check WCAG 2.x contrast ratio for foreground/background color pairs.

• Calculates precise contrast ratio per WCAG relative luminance formula
• Reports AA and AAA compliance for normal and large text
• Accepts hex (#fff, #ffffff), rgb(r,g,b), and named colors

validate_aria

Validate ARIA attributes on HTML elements.

• Detects invalid ARIA roles
• Checks for missing required ARIA properties per role
• Flags redundant ARIA roles that match native semantics
• Warns about aria-label on non-interactive elements
• Catches aria-hidden="true" on focusable elements

check_form_accessibility

Audit form elements for accessibility compliance.

• Verifies every input has an associated label (explicit, implicit, or ARIA)
• Checks radio/checkbox groups for <fieldset> and <legend>
• Flags placeholder text used as the only label
• Suggests autocomplete attributes for personal info fields
• Detects duplicate IDs that break label association

Setup

npm install
npm run build

Usage with Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "a11y-tools": {
      "command": "node",
      "args": ["D:/products/mcp-servers/mcp-a11y-tools/dist/index.js"]
    }
  }
}

License

MIT