No agent payment protocol beyond UCP

What it detects

The site has a UCP profile but supports no other agent payment protocol (e.g. x402, L402) alongside it.

Why it matters

This is a forward-looking, informational signal only — broader agent-payment protocol support widens the set of agents that can transact, but adoption of these secondary protocols is still small.

How to fix

- Check whether the site supports any agent payment protocol beyond UCP — e.g. an HTTP 402-style challenge for x402 (github.com/coinbase/x402) or L402 (docs.lightning.engineering). - This is optional/forward-looking: only invest here once the core UCP profile (checkout + signing keys) is solid, since adoption of these secondary protocols is still small. - If pursuing it, add a `402 Payment Required` response with a `WWW-Authenticate` challenge header on the relevant paid endpoint, following the x402 or L402 spec. - Verify: request the protected endpoint without payment credentials and confirm a spec-compliant `402` challenge response.

References

• Universal Commerce Protocol specification