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Accessibility Testing MCP

Accessibility Testing MCP

by joe-watkins
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Accessibility Testing MCP

An MCP server for accessibility testing using axe-core and IBM Equal Access. Choose your testing engine or use both for comprehensive coverage.

Example Prompts

  • "Test the accessibility of https://example.com"

  • "Test the accessibility of https://example.com" blockers only output issues in chat: What is the Issue, Who it Impacts, How to Fix, WCAG, Severity, Code Snippet"

Dual Engine Support

  • Axe-core (Deque) - Industry standard, zero false positives

  • IBM Equal Access - Comprehensive IBM accessibility requirements

Multi-Screen Testing

Test at multiple viewport sizes to catch responsive accessibility issues.

Tools

Tool

Description

analyze_url

Test any URL for accessibility issues

analyze_url_json

URL test with raw JSON output

analyze_html

Test HTML content directly

analyze_html_json

HTML test with raw JSON output

get_rules

List available accessibility rules

All tools accept an optional engine parameter ("axe" or "ace").

Related MCP server: Accessibility MCP Server

Installation

npm install
npm run build

Configuration

Environment Variables

Configure via MCP config env section:

Variable

Values

Default

Description

A11Y_ENGINE

axe, ace

axe

Testing engine

WCAG_LEVEL

2.0_A, 2.0_AA, 2.1_A, 2.1_AA, 2.2_AA, etc.

2.1_AA

WCAG version & level

BEST_PRACTICES

true, false

true

Include best practices/recommendations

SCREEN_SIZES

Comma-separated WIDTHxHEIGHT

1280x1024

Viewport sizes to test

HEADLESS_BROWSER

true, false

true

Run browser in headless mode; set to false to open visible browser

The WCAG_LEVEL setting automatically configures both Axe-core tags and IBM Equal Access policies.

VS Code (GitHub Copilot)

Add to VS Code settings (JSON):

"mcp": {
  "servers": {
    "accessibility-testing-mcp": {
      "type": "stdio",
      "command": "node",
      "args": ["/path/to/accessibility-testing-mcp/build/index.js"],
      "env": {
        "A11Y_ENGINE": "axe",
        "WCAG_LEVEL": "2.2_AA",
        "BEST_PRACTICES": "true",
        "SCREEN_SIZES": "1280x1024,320x640",
        "HEADLESS_BROWSER": "true"
      }
    }
  }
}

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "accessibility": {
      "command": "node",
      "args": ["/path/to/accessibility-testing-mcp/build/index.js"],
      "env": {
        "A11Y_ENGINE": "ace",
        "WCAG_LEVEL": "2.2_AA",
        "BEST_PRACTICES": "true"
      }
    }
  }
}

Understanding Results

Axe-core Output

  • Violations: Definite accessibility failures

  • Incomplete: Needs manual review

  • Passes: Rules that passed

  • Inapplicable: Rules that don't apply

IBM Equal Access Output

  • Violations: Accessibility failures

  • Potential Violations: Needs review

  • Recommendations: Suggested improvements (when BEST_PRACTICES=true)

  • Manual Checks: Requires human testing

WCAG_LEVEL Values

Level

Description

2.0_A

WCAG 2.0 Level A

2.0_AA

WCAG 2.0 Level AA

2.1_A

WCAG 2.1 Level A

2.1_AA

WCAG 2.1 Level AA (default)

2.1_AAA

WCAG 2.1 Level AAA

2.2_A

WCAG 2.2 Level A

2.2_AA

WCAG 2.2 Level AA

2.2_AAA

WCAG 2.2 Level AAA

Dependencies

  • @modelcontextprotocol/sdk - MCP server framework

  • axe-core - Deque accessibility testing engine

  • accessibility-checker - IBM Equal Access engine

  • playwright - Headless browser automation

License

MIT

Available Tools

5 tools
analyze_htmlB

Run accessibility tests on raw HTML content. [Engine: axe, WCAG: 2.1_AA, Screens: 1280x1024]

Inputs: html (required), tags, engine.

analyze_html_jsonA

Run accessibility tests on raw HTML content and return violations in raw JSON format. [Engine: axe, WCAG: 2.1_AA, Screens: 1280x1024]

Inputs: html (required), tags, engine.

analyze_urlB

Run accessibility tests on a URL and return detailed violation reports. [Engine: axe, WCAG: 2.1_AA, Screens: 1280x1024]

Inputs: url (required), tags, engine.

analyze_url_jsonA

Run accessibility tests on a URL and return violations in raw JSON format. [Engine: axe, WCAG: 2.1_AA, Screens: 1280x1024]

Inputs: url (required), tags, engine.

get_rulesA

Get information about available accessibility rules for the specified engine. [Engine: axe, WCAG: 2.1_AA, Screens: 1280x1024]

Inputs: tags, engine.

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

Loading tool schema changelog…

    Deploy Server
    One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

    TDQS

    A3.7/5.0

    Scored across 5 tools

    Disambiguation4/5

    The tools are clearly separated by input type (URL vs HTML) and output format (detailed report vs raw JSON). The _json suffix disambiguates the output format, but analyze_url and analyze_url_json are conceptually similar, which could cause minor selection confusion.

    Naming Consistency5/5

    All tool names follow a consistent verb_noun pattern with snake_case. The analyze_* prefix is used for testing actions, and get_rules follows the same convention, making the naming predictable and uniform.

    Tool Count5/5

    With 5 tools, the set is well-scoped for the server's purpose of accessibility testing. Each tool serves a distinct input/output combination without unnecessary bloat, and the count is within the ideal range.

    Completeness4/5

    The server covers the core workflows of accessibility testing: analyzing URLs and HTML, with both human-readable and JSON output, plus rule discovery. Minor gaps exist, such as lack of customizable WCAG versions or screen sizes, but the essential surface is complete.

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