Protocol
MEDIUMEvery service `version` matches YYYY-MM-DD
Each `services[].version` matches the ISO-date pattern `YYYY-MM-DD`. Free-form version labels like `1.0` or `latest` defeat the version-pinning agents rely on, leaving them unable to negotiate the correct spec generation.
What this check looks for
UCP services advertise the spec generation they conform to using an ISO-date `version` string. Agents pin against that date to know which schema and transport rules apply. We require every service's `version` to match `/^\d{4}-\d{2}-\d{2}$/`; missing or free-form labels fail.
Which AI surfaces it affects
- Google AI Mode (UCP)80
- Microsoft Copilot60
- ChatGPT (ACP)20
- Perplexity20
- Meta AI20
Weighted against the live specs — ACP 2026-04-17, UCP 2026-04-08.
How to fix it
Use ISO-date `version` strings on every service
Shopify
Developer- Update the UCP JSON your handler emits — set every service `version` to the YYYY-MM-DD spec date.
BigCommerce
Developer- Update the edge worker producing the UCP profile to use ISO-date service versions.
WooCommerce
A few minutes- Edit the UCP JSON to use ISO-date `version` strings on each service.
Custom / headless
A few minutes- Replace free-form versions with `YYYY-MM-DD` dates on every services[] entry.
<!-- /.well-known/ucp (excerpt) -->
{
"services": [
{
"namespace": "shopping",
"version": "2026-04-08",
"transport": "rest",
"endpoint": "https://example.com/ucp/shopping"
}
]
}The spec it's pinned to
UCP overview — versioned services
UCP services declare their spec generation via an ISO-date `version` (e.g., `2026-04-08`). Free-form labels like `1.0` or `latest` defeat the version-pinning agent negotiation depends on.
Does your store pass this check?
Run the full audit — 82 checks across five AI shopping surfaces. Most tools only check whether you get mentioned; we check whether an agent can buy from you.