The order has to be specific
A proposed purchase includes exact items, quantities, fulfillment, taxes, discounts and terms. A commerce integration must account for changes while the shopper is deciding. Ask what happens when inventory changes, a delivery option becomes unavailable or a required customer choice is missing. A checkout link in HTML establishes only that a link exists.
Keep responsibilities explicit
Identify the merchant of record and which service owns the checkout session, payment processing, fulfillment and support. A protocol can describe interactions while a platform decides what is enabled for an account. Compare the actual integration route and version rather than a generic protocol badge.
Test in the right environment
Use official sandboxes and approved merchant tools for transaction validation. The public L0 scanner deliberately does not visit cart or checkout endpoints, submit forms or attempt a purchase. Its result should direct you to the missing evidence, not imply that checkout passed.