Protocol
HIGHEach service satisfies the transport-conditional field requirements
rest/mcp services declare `endpoint` + `schema`; a2a declares `endpoint`; embedded declares `schema`. A service declared with the right transport but missing endpoint/schema is unreachable — agents can't negotiate or connect.
What this check looks for
Each UCP transport implies its own minimum field set. REST and MCP services advertise both a runtime `endpoint` (where agents connect) and a `schema` URL (machine-readable contract). A2A services need at least the `endpoint`. `embedded` services declare only the `schema` (the runtime is the agent itself). Missing fields make the service unreachable.
Which AI surfaces it affects
- Google AI Mode (UCP)80
- Microsoft Copilot60
- ChatGPT (ACP)30
- Perplexity20
- Meta AI20
Weighted against the live specs — ACP 2026-04-17, UCP 2026-04-08.
How to fix it
Populate the conditional fields required by each service's transport
Shopify
Developer- Update the UCP JSON: every rest/mcp service needs endpoint + schema; a2a needs endpoint; embedded needs schema.
BigCommerce
Developer- In the edge worker producing UCP, set endpoint and schema for rest/mcp entries; endpoint for a2a; schema for embedded.
WooCommerce
Developer- Edit the UCP JSON to populate endpoint/schema per the transport rules above.
Custom / headless
Developer- For each services[] entry, fill in the fields its transport requires.
<!-- /.well-known/ucp (excerpt) -->
{
"services": [
{
"namespace": "shopping",
"version": "2026-04-08",
"transport": "rest",
"endpoint": "https://example.com/ucp/shopping",
"schema": "https://example.com/ucp/shopping/openapi.json"
},
{
"namespace": "fulfilment",
"version": "2026-04-08",
"transport": "a2a",
"endpoint": "https://example.com/ucp/fulfilment"
},
{
"namespace": "widget",
"version": "2026-04-08",
"transport": "embedded",
"schema": "https://example.com/ucp/widget/manifest.json"
}
]
}The spec it's pinned to
UCP overview — transport-conditional fields
Per the UCP overview, each transport implies its own required fields: `rest` and `mcp` need both `endpoint` and `schema`; `a2a` needs `endpoint`; `embedded` needs `schema`. Missing fields make the service unreachable for agents.
Does your store pass this check?
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