validate_accessibility_axe
Analyze website accessibility using Axe to identify WCAG compliance issues with zero false positives, helping developers improve web accessibility.
Instructions
Analyze website accessibility using Axe. Free, open-source, finds ~57% of WCAG issues with zero false positives.
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| url | Yes | ||
| wcagLevel | No | WCAG level (wcag2a, wcag2aa, wcag2aaa, wcag21aa, wcag22aa) |
Implementation Reference
- src/accessibility/axe.ts:44-126 (handler)The core handler function `analyzeAxe` that launches a headless Chromium browser using Playwright, navigates to the URL, injects the axe-core library, runs WCAG-specific accessibility tests, processes violations by impact level, and returns structured results including counts and detailed issues.
export async function analyzeAxe( url: string, options: AxeOptions = {} ): Promise<AxeResult> { let browser: Browser | null = null; let page: Page | null = null; try { // Launch browser browser = await chromium.launch({ headless: true }); page = await browser.newPage(); // Navigate to page await page.goto(url, { timeout: options.timeout || 60000, waitUntil: 'networkidle' }); // Inject axe-core await page.addScriptTag({ url: 'https://cdnjs.cloudflare.com/ajax/libs/axe-core/4.10.2/axe.min.js', }); // Run axe analysis const wcagLevel = options.wcagLevel || 'wcag2aa'; const results = await page.evaluate((level) => { return (window as any).axe.run({ runOnly: { type: 'tag', values: [level], }, }); }, wcagLevel); await browser.close(); // Count violations by severity const critical = results.violations.filter((v: any) => v.impact === 'critical').length; const serious = results.violations.filter((v: any) => v.impact === 'serious').length; const moderate = results.violations.filter((v: any) => v.impact === 'moderate').length; const minor = results.violations.filter((v: any) => v.impact === 'minor').length; // Format violations const issues: AxeViolation[] = results.violations.map((v: any) => ({ id: v.id, impact: v.impact, description: v.description, helpUrl: v.helpUrl, nodes: v.nodes.length, })); return { tool: 'axe', success: true, url, wcagLevel, violations: results.violations.length, critical, serious, moderate, minor, passes: results.passes.length, incomplete: results.incomplete.length, issues, }; } catch (error) { if (browser) { await browser.close(); } return { tool: 'axe', success: false, url, wcagLevel: options.wcagLevel || 'wcag2aa', violations: 0, critical: 0, serious: 0, moderate: 0, minor: 0, passes: 0, incomplete: 0, issues: [], error: error instanceof Error ? error.message : String(error), }; } } - index.ts:188-199 (registration)MCP tool registration defining the tool name, description, and input schema for the validate_accessibility_axe tool.
{ name: 'validate_accessibility_axe', description: 'Analyze website accessibility using Axe. Free, open-source, finds ~57% of WCAG issues with zero false positives.', inputSchema: { type: 'object', properties: { url: { type: 'string' }, wcagLevel: { type: 'string', description: 'WCAG level (wcag2a, wcag2aa, wcag2aaa, wcag21aa, wcag22aa)' }, }, required: ['url'], }, }, - index.ts:61-64 (schema)Zod validation schema for the tool's input arguments, ensuring URL is valid and wcagLevel is optional string.
const AxeArgsSchema = z.object({ url: z.string().url(), wcagLevel: z.string().optional(), }); - index.ts:362-368 (handler)Dispatcher case in the main MCP callToolRequest handler that validates arguments and delegates to the analyzeAxe implementation.
case 'validate_accessibility_axe': { const validatedArgs = AxeArgsSchema.parse(args); const result = await analyzeAxe(validatedArgs.url, { wcagLevel: validatedArgs.wcagLevel, }); return { content: [{ type: 'text', text: JSON.stringify(result, null, 2) }] }; }