Protocol
HIGH/.well-known/ucp response Content-Type is application/json
The `/.well-known/ucp` response declares `Content-Type: application/json`. Agent runtimes that gate parsing on Content-Type will skip your profile if it's served as HTML or plain text.
What this check looks for
Lightweight agent clients route response handling by Content-Type. A profile served with `text/html` (because a frontend framework intercepts the request) or `text/plain` (because the file was uploaded with no MIME mapping) will be silently skipped. We require the media type to start with `application/json`. Transport metadata for this check is populated by the v2 runner (Task I1); until then the check returns `na`.
Which AI surfaces it affects
- Google AI Mode (UCP)100
- Microsoft Copilot70
- ChatGPT (ACP)30
- Meta AI30
- Perplexity20
Weighted against the live specs — ACP 2026-04-17, UCP 2026-04-08.
How to fix it
Serve /.well-known/ucp with `Content-Type: application/json`
Shopify
Developer- If you serve `/.well-known/ucp` via a Shopify page template, switch to an edge handler that sets Content-Type explicitly — Shopify page responses are text/html.
BigCommerce
Developer- Use a Cloudflare Worker (or your CDN's edge function) to attach `Content-Type: application/json` to the response.
WooCommerce
Developer- Add a MIME mapping to your webserver for the `/.well-known/ucp` route, or use a PHP handler that sets `header("Content-Type: application/json")` before output.
Custom / headless
Developer- Set the response `Content-Type` to `application/json` (`charset=utf-8` parameter is fine).
HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Cache-Control: public, max-age=3600
{ "version": "2026-04-08", ... }The spec it's pinned to
UCP overview — JSON profile media type
The UCP overview defines the profile as a JSON document. Agent runtimes that gate parsing on `Content-Type` will skip a profile served with `text/html` or `text/plain`.
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