ACP: How Does an Agent Connect to Merchant Shopping and Checkout?

You ask a shopping agent to find a coffee machine. Once it finds one, the purchase has only begun: is it in stock, what is shipping, is a coupon valid, what did the user approve and how does the merchant receive the order and payment information?

The Agentic Commerce Protocol (ACP) specifies programmatic commerce interactions between agents and merchants. Its scope extends beyond a payment to product information, checkout status, payment credential handoff and order updates.

The coffee machine is hypothetical. This interpretation is based on official materials; no merchant integration or real transaction was tested. Sources reviewed October 28, 2026.

sequenceDiagram participant U as User participant A as Shopping agent or platform participant M as Merchant system participant P as Merchant payment provider U->>A: Find a coffee machine A->>M: Request product and inventory M-->>A: Return product and terms A->>M: Create and update checkout session M-->>A: Return price, shipping, tax and status A->>U: Present final details for approval U->>A: Approve purchase A->>M: Complete checkout with applicable payment information M->>P: Process through merchant payment flow M-->>A: Return order and subsequent status

In OpenAI’s published Agentic Checkout integration, merchants implement interfaces to create, update and complete checkout sessions, return authoritative cart information including fees, delivery and status, and synchronize order updates through events. Merchants continue using their payment services and settlement arrangements. Delegated payment depends on the integration. See OpenAI’s checkout specification.

Why not just send a product link?

A link can send a person to the merchant, but a machine completing a purchase within a unified experience needs structured information. An $80 product can incur shipping and tax or receive a discount; after an address changes, the merchant needs to recalculate.

Information	Best source	Why synchronize?
Price, stock and restrictions	Merchant	Search results can be stale
Shipping, taxes and discounts	Merchant and commerce systems	Final price can change with address or promotion
User confirmation	User and platform	The user must see what is being bought and for how much
Payment and order status	Merchant and payment provider	The user needs outcome and fulfillment updates

The merchant system remains a key source of product, checkout and fulfillment state. The agent should display the latest checkout information.

How are payment credentials handed off?

In applicable implementations, ACP delegated payment can convey payment capability through a limited payment token, which the merchant processes with a compatible provider. Generation, processor support and restrictions depend on implementation and region. Tokens can reduce exposure of raw payment information in some flows, but remain sensitive payment credentials. See the ACP specification.

ACP support does not guarantee traffic

The ACP site explains that access to a particular AI platform remains subject to that platform’s participation process; merchants may also decide whether to accept transactions. OpenAI’s commerce documentation distinguishes an open protocol from eligibility for a particular ChatGPT shopping feature.

Before integration, ask how the catalog updates, who calculates the final price, how failures and duplicate requests are handled, who manages refunds and support, which processors accept the token, and whether platform approval is required. ACP supplies a shared checkout language; product quality, merchant trust and fulfillment still depend on the product and merchant.

Further reading: ACP, open specification and OpenAI checkout specification.