Axe Accessibility Testing Skill

Automated testing via the axe-a11y MCP server. Not a framework, not a manual-testing helper — the server executes automated scans and returns actual WCAG violation JSON.

What This Skill Runs Under the Hood

• Real Google Chrome Stable installed inside the container (not Playwright-bundled Chromium)
• Patchright — a Playwright fork that patches CDP-level detection leaks, so bot walls (Amazon, Cloudflare, DataDome, Akamai) don't fire on well-known Playwright signals
• Persistent Chrome profile bind-mounted from the host — cookies + Login Data survive container restarts, so authenticated audits work after a one-time manual sign-in
• Xvfb + VNC on :5900 — Chrome is headed (headed is required for realistic fingerprinting); operators can watch it via VNC
• axe-core WCAG 2.0/2.1 A/AA/AAA compliance checking with node-level details and remediation guidance

Tools

You have access to the following tools via the axe-a11y MCP server:

1. audit_page

Run a full accessibility audit on a given URL.

• Inputs: url (required), tags (optional, e.g. ["wcag2aa"]), include_passes (optional boolean), ignore_https_errors (optional boolean)
• Use when: You need a comprehensive list of accessibility violations on a page.

2. check_specific_rules

Check specific axe-core rules on a page.

• Inputs: url (required), rules (required, e.g. ["color-contrast", "image-alt"]), ignore_https_errors (optional boolean)
• Use when: You are testing for a small set of targeted issues.

3. audit_element

Audit a specific element on the page by CSS selector.

• Inputs: url (required), selector (required), ignore_https_errors (optional boolean)
• Use when: You want to test a single component, like a navigation menu or form.

4. get_wcag_summary

Get a high-level WCAG compliance summary.

• Inputs: url (required), ignore_https_errors (optional boolean)
• Use when: You want a quick pass/fail summary without all node-level details.

5. axe_capture_page

Capture a rendered screenshot of the page.

• Inputs: url (required), full_page (optional boolean), wait_for_selector (optional string), wait_for_text (optional string), ignore_https_errors (optional boolean)
• Use when: You need visual proof of what the browser actually rendered.

6. axe_capture_element

Capture a screenshot of a specific element.

• Inputs: url (required), selector (required), ignore_https_errors (optional boolean)
• Use when: You want evidence focused on one component.

7. record_page_session

Record a short browser session video.

• Inputs: url (required), duration_ms (optional integer), capture_final_screenshot (optional boolean), ignore_https_errors (optional boolean)
• Use when: You want to diagnose delayed rendering, lazy-loaded assets, or login transitions.

8. generate_pdf

Generate a PDF export of the rendered page.

• Inputs: url (required), format (optional: a4/a3/a5/letter/legal/tabloid/custom), landscape (optional boolean), print_background (optional boolean), margin (optional object), page_ranges (optional string), ignore_https_errors (optional boolean)
• Use when: You need a printable capture of the fully rendered page for reports, handoff, or archival.

9. capture_network

Capture page-load network activity and optionally export HAR.

• Inputs: url (required), export_format (optional: summary or har), ignore_https_errors (optional boolean)
• Use when: You need request/response counts, status breakdowns, content-type summaries, or a HAR artifact for deeper debugging.

Artifact Access

Tools that generate files return *_artifact_url fields. Always use the exact URL returned by the tool instead of rewriting the host manually.

The artifact URL host is derived from the MCP endpoint used for the request:

• Host-local MCP calls return host-local artifact URLs such as http://127.0.0.1:9010/...
• browser-sandbox MCP calls return sandbox-compatible artifact URLs such as http://host.docker.internal:9010/...

Example:

{
  "pdf_artifact_url": "http://host.docker.internal:9010/artifacts/pdfs/example-com-export-123.pdf"
}

From browser-sandbox:

curl -o report.pdf "http://host.docker.internal:9010/artifacts/pdfs/example-com-export-123.pdf"

If artifact download returns 403 from the sandbox, re-sync the live skill and OpenShell policy:

./scripts/bring-up.sh

Reporting Guidelines

IMPORTANT: When presenting accessibility audit results to users:

• ✅ Present this as an automated accessibility scan
• ✅ State that this uses axe-core with real Google Chrome under patchright — production browser automation
• ✅ Report actual violations found with specific details and remediation guidance
• ✅ Clarify that automated tools like axe-core typically catch ~57% of WCAG issues automatically. Mention that manual evaluation is required for comprehensive conformance.
• ✅ Explicitly review and return incomplete items reported by the server, as these require human verification.

If a site returns an error, a bot-wall page, or a login screen, the recovery path is node src/manual-login.js <url>, not adding a disclaimer.

Best Practices

1. Certificate errors: If a site has certificate issues, use ignore_https_errors: true.
2. Wait for dynamic portals: The server navigates with load, then waits for visible images and optional selectors/text. For dynamic pages, provide wait_for_selector or wait_for_text.
3. Start broad, then zoom in: Use get_wcag_summary first, then audit_page or check_specific_rules for detail.
4. Authenticated sites: The persistent profile is disabled by default. When testing sites behind login, enable it via AXE_A11Y_PROFILE_ENABLED=true in .env and run node src/manual-login.js <url> once via VNC — subsequent audits reuse that session automatically.
5. Use returned artifact URLs as-is: Do not replace the host with localhost or host.docker.internal unless you are intentionally changing where the request originates.