A11y MCP Server

a11y-mcp-server

MCP server for accessibility auditing, WCAG criteria lookup, and remediation guidance.

Features

• a11y_lookup_wcag: Look up WCAG 2.2 criteria by number, keyword, or level
• a11y_check_pattern: Analyze HTML snippets for common accessibility issues
• a11y_suggest_fix: Get remediation patterns with before/after code examples
• a11y_document_component: Generate accessibility docs for 18+ UI component types
• a11y_audit_summary: Generate professional audit reports from issues list

Local Development

# Install dependencies
npm install

# Build
npm run build

# Run locally
npm start

# Server runs on http://localhost:8080
# Health check: http://localhost:8080/health
# MCP endpoint: http://localhost:8080/mcp

NFSN Deployment

Prerequisites

1. NFSN account with funds (~$10 initial deposit)
2. SSH access configured

Setup Steps

1. Create NFSN Site

1. Log into NFSN Members Interface
2. Sites → Create a New Site
3. Site type: Custom (required for Node.js daemon)
4. Note your site hostname (e.g., yoursite.nfshost.com)

2. Upload Code

# From project directory
rsync -avz --exclude node_modules --exclude .git --exclude dist \
  ./ USERNAME_SITENAME@ssh.phx.nearlyfreespeech.net:/home/protected/a11y-mcp-server

3. SSH Setup

ssh USERNAME_SITENAME@ssh.phx.nearlyfreespeech.net

# Navigate to project
cd /home/protected/a11y-mcp-server

# Check Node.js version (should be 18+)
node --version

# Install dependencies
npm install --production

# Build
npm run build

# Make run.sh executable
chmod +x run.sh

# Test locally
./run.sh
# Ctrl+C to stop

4. Configure NFSN Daemon

1. Go to NFSN site control panel
2. Sites → Your Site → Site Information → Daemons
3. Add daemon:
   • Tag: node
   • Command Line: /home/protected/a11y-mcp-server/run.sh
   • Working Directory: /home/protected/a11y-mcp-server

5. Configure NFSN Proxy

1. Sites → Your Site → Site Information → Proxies
2. Add proxy:
   • Protocol: http
   • Base URI: /mcp
   • Document Root: (leave empty)
   • Target Port: 8080

6. Verify Deployment

# Check health endpoint
curl https://yoursite.nfshost.com/health

# Test MCP endpoint
curl -X POST https://yoursite.nfshost.com/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","method":"tools/list","id":1}'

Troubleshooting

Check daemon logs:

ssh USERNAME_SITENAME@ssh.phx.nearlyfreespeech.net
cat /home/protected/a11y-mcp-server/daemon.log

Restart daemon: Via NFSN control panel: Sites → Daemons → Restart

Check if daemon is running:

ps aux | grep node

Claude Code Configuration

Add to ~/.config/claude/claude_desktop_config.json:

{
  "mcpServers": {
    "a11y": {
      "url": "https://yoursite.nfshost.com/mcp"
    }
  }
}

Then restart Claude Code.

Local Testing with Claude Code

For testing before NFSN deployment, run the server locally and configure Claude Code to connect:

1. Start the server:

npm start

2. Add to ~/.config/claude/claude_desktop_config.json:

{
  "mcpServers": {
    "a11y-local": {
      "url": "http://localhost:8080/mcp"
    }
  }
}

3. Restart Claude Code

Evaluation Questions

Use these questions to verify the server is working correctly:

1. WCAG Lookup: "What WCAG criterion covers keyboard navigation and what level is it?"

   • Expected: Returns 2.1.1 Keyboard (Level A) with full details

2. Remediation Pattern: "What's the remediation pattern for missing alt text on decorative images?"

   • Expected: Returns pattern with empty alt="" example

3. Component Documentation: "Generate accessibility documentation for a modal dialog component."

   • Expected: Returns keyboard interactions, ARIA attributes, screen reader expectations

4. WCAG 2.2 Search: "Which WCAG 2.2 criteria are specific to mobile/touch interactions?"

   • Expected: Returns 2.5.x Input Modalities criteria

5. Common Failures: "What are the common failures for criterion 1.4.3 Contrast?"

   • Expected: Returns F24, F83 failure techniques

Usage Examples

Look up WCAG criterion

Query: "What WCAG criterion covers keyboard navigation?"
Tool: a11y_lookup_wcag
Args: { "query": "keyboard" }

Check HTML for issues

Query: "Check this HTML for accessibility issues"
Tool: a11y_check_pattern
Args: { "html": "<button><svg>...</svg></button>" }

Get remediation pattern

Query: "How do I fix missing alt text on decorative images?"
Tool: a11y_suggest_fix
Args: { "issueType": "missing-alt-decorative" }

Generate component docs

Query: "Generate accessibility documentation for a modal dialog"
Tool: a11y_document_component
Args: { "componentType": "modal" }

Updating WCAG Data

WCAG criteria are bundled in `src/data/wcag-criteria.