AP2: Agent Payments Protocol
Google's sister protocol to UCP. AP2 handles secure agent-led payments while UCP orchestrates the broader purchase lifecycle.
In detail
Where ACP carries its payment layer through Stripe's Shared Payment Token and the Delegate Payment endpoint at POST /agentic_commerce/delegate_payment, the Google stack separates payments cleanly. UCP handles checkout-lifecycle: POST /checkout-sessions, PUT updates, completion, cancel. AP2 handles the credential layer that funds the completion.
The separation matters operationally. A merchant implementing UCP does not also need to design payment-instrument handling from scratch; AP2 provides the contract, and supported PSPs implement against it. For a Shopify brand using Shopify Agentic Storefronts, both layers are wrapped inside the channel — the merchant does not touch UCP or AP2 directly.
Why it matters
The clean split between protocol-layer and payments-layer is what lets the Google stack support multiple PSPs without rewriting UCP. For Shopify brands, the practical implication is that the payments side of agentic commerce is not under their control — it lives between Google, the PSP, and the buyer's payment instrument. The merchant's job is the catalog, the feed, the endpoints, and the fulfillment.
Related terms
- UCP (Universal Commerce Protocol) — the lifecycle protocol AP2 pairs with.
- ACP (Agentic Commerce Protocol) — the OpenAI/Stripe/Meta counterpart that bundles its own payments layer.
- Vault token (vs SPT) — the equivalent artifact on the ACP side.
- Shopify Agentic Storefronts — wraps both UCP and AP2 for Shopify merchants.
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Frequently asked questions
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