Agentic Commerce Protocol payment validation

What the protocol establishes

ACP lets compatible applications and sellers complete programmatic checkouts while the seller remains responsible for payment processing and fulfillment. The merchant should separately prove that the final checkout matches user-approved intent.

Five checks before execution

1. Validate the checkout session and current cart version.
2. Bind the final total and currency to customer-approved limits.
3. Confirm merchant identity and permitted fulfillment context.
4. Keep payment credentials with the existing payment provider.
5. Consume the payment attempt once and retain a minimal receipt.

The gap MandateShield closes

A valid checkout session does not prove that the customer approved every later cart, shipping or price change.

MandateShield normalizes execution facts and returns a deterministic decision with exact findings and a tamper-evident receipt. It complements protocol-native signature verification; it does not replace it.