UCP: 42,575 websites publish a commerce profile an agent can read

What is UCP?

The Universal Commerce Protocol is an open standard that lets a business publish, at /.well-known/ucp, a machine-readable profile of what it offers an agent: its services, its capabilities such as checkout and catalogue search, its payment handlers, and the transports it speaks, including REST, MCP and A2A. The specification is versioned by date; the current one is 2026-04-08 and is governed by the UCP Tech Council. Shopify and Wix advertise the MCP endpoint they run for every store through this profile, which is how the September census found 96 live endpoints that no MCP server card mentioned.

How does Known Good check it?

The probe fetches /.well-known/ucp on the site's own domain, after robots.txt, and reads it. A profile counts when it parses and declares at least one capability. If it names an MCP endpoint, the probe knocks once on that endpoint with initialize and tools/list, the same knock it gives any server, and records whether the tool list came back. Nothing in the profile is taken on trust: a declared capability is recorded as declared, an answering endpoint as answering, and the two are counted separately.

How many websites publish UCP?

Measured on 28 Sep 2026Sites

Publish a /.well-known/ucp profile that parses and declares a capability42,575

Profile names an MCP endpoint41,643

That endpoint returns its tool list41,424

Endpoint is platform-supplied (rubric v1.2)41,354

Profile declares checkout42,437

Could not ask (robots.txt at the profile path)102

Refused at the profile path (401/403 1,350; 402 141; other 767: 429 484, 5xx 156, no answer 127)2,258

1,244 hosts answered 200 at /.well-known/ucp only after a redirect at the profile path; none of the 41,424 answering endpoints depended on one.

On 451 hosts the storefront settled on another domain, and the probe asked at the address it was given; 80 of the 41,424 answering endpoints come from them.

Does a UCP profile make a site agent-ready?

On its own, no. Under rubric v1.2 a site is listed on at least one strong signal and at least two signals in all, and a profile is a declaration, not a signal. The endpoint the profile names can list the site, if it answers; the profile is the route the probe took to find it. Until 4 Oct 2026 the route itself had been treated as a sign that a platform ran the server; it is not, and 49 sites moved from platform-supplied to self-built when that criterion was withdrawn.

How do I add UCP to my site?

Publish a JSON profile at /.well-known/ucp that follows the 2026-04-08 schema, declare only capabilities you serve, and name the MCP endpoint if you run one. Then ask for a probe at /submit; the report page will show the knock and the date.

Changelog

DateChange

13 Oct 2026Corrected. The capabilities of 4 hosts were read from the redirect in front of their profile instead of the body that answered. Re-read, the count rises by 3: profiles that declare a capability, 42,572 → 42,575; profiles that declare checkout, 42,434 → 42,437.

Frequently asked

Is UCP the same as an MCP server? No. UCP is a profile that can point at an MCP server; the server is what answers.

Does Known Good list a site for its UCP profile? No. It lists a site for an endpoint or file that answered.

Who runs the Shopify and Wix endpoints the profiles point at? The platforms. The report page labels those servers platform-supplied under rubric v1.2.

Counts are of sites (hostnames), measured by Known Good's probe on 28 Sep 2026. Could-not-ask is counted beside the total, never inside it. Method: /bot. Rubric: /benchmark.

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