your 404 page has a blind spot

Han Wang reported last month that AI agents account for 48% of docs visitors across Mintlify-powered sites.

Docs teams design 404 pages for visual recovery. They add an illustration, a search bar, a homepage link, and recommended pages. An agent gets page content with no useful route forward. It reports the failure or invents a plausible answer.

I built agent404.dev to give agents a recovery path. Add one script tag:

<script
  src="https://agent404.dev/agent-404.min.js"
  data-site-id="your-site-id"
  data-api-key="your-api-key"
  defer
></script>

Agent 404 indexes your live pages in the background. On a 404, it compares the dead URL with that index and returns ranked suggestions in a human-readable list and schema.org JSON-LD.

It catches several common failures:

• Hallucinated URLs: an agent invents auth0.com/docs/customize/login-pages/acul while the real path is /advanced-customizations.
• Typos: docs.stripe.com/payment/checkout points nowhere because the path uses /payments/checkout.
• Docs restructures: Next.js moved its static export docs to /docs/app/guides/static-exports, leaving old links behind.
• Path renames: Vercel moved Edge Functions from /docs/edge-functions/overview to /docs/functions.
• Subtree moves: Supabase shifted auth docs from /docs/auth/ to /docs/guides/auth.
• Missing segments: an agent links to react.dev/reference/hooks and drops the /react/ segment.

The demo covers more cases.

These failures produce no support ticket. Agent 404 points the agent to a live page before it gives up or guesses.

The project is open source, MIT licensed, and under 3 KB. You can self-host it on Vercel or Cloudflare Workers, or use agent404.dev.