Agentic commerce
ACP (Agentic Commerce Protocol)
ACP is a specification from OpenAI and Stripe defining how merchants expose product feeds and checkout sessions so an AI agent can complete a purchase.
The April 2026 revision covers checkout, payment delegation, cart, feed and authentication, plus an integration hook that lets ACP-aware agents advertise their checkout capability through MCP tool discovery.
Its scope narrowed during 2026: OpenAI shut down Instant Checkout and repositioned ACP toward product discovery and merchant-controlled experiences rather than in-chat purchase completion. Major retailers including Target, Sephora, Nordstrom, Best Buy and Wayfair adopted it on the discovery side.
What the specification actually names
ACP is the most commerce-specific of the protocols in this space, and the easiest way to hold it in mind is as a list of objects rather than as a philosophy. The April 2026 revision covers a product feed, a checkout session, payment delegation, cart and authentication, plus an integration hook that lets an ACP-aware agent advertise its checkout capability through MCP tool discovery.
Each object exists because a step a person performs in a browser has no machine equivalent. A person browses a catalog; an agent needs a feed. A person watches a total assemble as they type an address; an agent needs a session that returns a binding number. A person types a card into a form on your domain; an agent needs a defined way to hand payment to your processor without holding the credential itself.
The publishers are OpenAI and Stripe, and that pairing is visible in the shape of the document. It is written by a party that owns an assistant surface and a party that owns payment processing, and most of what it specifies is the boundary between the two.
| Object | The human equivalent | What the merchant has to provide |
|---|---|---|
| Product feed | Browsing the catalog | Accurate price, availability and identifiers, kept current |
| Checkout session | Filling in the checkout form | An endpoint returning a binding total including shipping and tax |
| Payment delegation | Typing a card into your form | A path for the agent environment to hand processing to your processor |
| Authentication | Being signed in | A way to establish which agent is calling, and on whose behalf |
| MCP discovery hook | Seeing that a buy button exists | A tool declaration an agent can find before it attempts anything |
Where ACP sits relative to UCP, AP2 and MCP
The four names are usually presented as a standards war, which leads merchants to the wrong conclusion — that the sensible move is to wait for a winner. They answer different questions and largely compose.
MCP, published by Anthropic, is the general mechanism by which an agent learns that a capability exists and how to call it; it says nothing about carts or money. UCP, from Google and Shopify, covers catalog reads and cart construction. ACP covers checkout execution and payment delegation. AP2, initiated by Google and donated to the FIDO Alliance in April 2026, covers proving that a specific human authorized a specific payment.
Sponsorship explains the coverage in every case. Google and Shopify need agents to be able to read the world's catalogs, so their standard specifies discovery. OpenAI and Stripe need a purchase to complete somewhere, so theirs specifies checkout and payment. Nobody has written a specification for a layer they did not already own.
The one overlap worth knowing is the cart boundary, where UCP and ACP both have something to say. The merchant-side requirement underneath is identical either way — a catalog carrying real price and real availability — which is why that piece of work is the only part of the stack that is not a wager on which standard prevails.
Payment delegation is the genuinely new part
Product feeds are not new and checkout endpoints are not new. The element of ACP with no prior equivalent is the delegation of payment: the agent's environment hands processing to the merchant's processor rather than holding card credentials or becoming the merchant of record itself.
That arrangement is what makes the protocol acceptable to merchants at all. You keep the processor relationship, the settlement and the customer record. You also keep the liability, and that is the half worth reading twice — an agent-initiated purchase and a human-initiated one reach your processor over the same rails, while the dispute evidence formats that exist today all assume a person was present at the transaction.
That gap is precisely what AP2 was written to close, and it is not addressed at the ACP layer. A merchant accepting agent-initiated payments now is accepting them without a standard artifact establishing what the cardholder authorized or within what limits.
What ACP does not specify
Reading a specification for what it omits is usually more informative than reading it for what it contains, and the omissions here are large enough to change what the phrase "ACP support" can honestly mean.
They also draw the line between shipping the prerequisites and implementing the protocol. A machine-readable catalog, a scoped agent gateway and a set of MCP tools are things ACP assumes a merchant already has. Having them is groundwork rather than conformance, and a platform presenting the two as the same claim is overstating what it does.
What the specification leaves entirely to you:
- Trust. Nothing in it decides which agents you should serve, or on what terms. That is a policy you write and enforce yourself.
- Authorisation and audit. It defines no permission scopes, no idempotency requirement and no audit record. An agent retrying an ambiguous request is an ordinary event, and nothing in the protocol prevents that becoming two orders.
- The post-purchase half. Returns, refunds, cancellations, subscription changes and support sit outside its scope, and that is where most of the operating cost of an order actually lives.
- Adoption. A conformant implementation does not oblige any assistant to use it. Which surfaces read what, in which categories, is a commercial matter no specification settles.
Frequently asked questions
- What is the Agentic Commerce Protocol?
- ACP is a specification published by OpenAI and Stripe defining how a merchant exposes a product feed and a checkout session so an AI agent can complete a purchase, including how payment processing is delegated to the merchant's own processor. Its April 2026 revision also covers cart, authentication and a hook that advertises checkout capability through MCP tool discovery.
- What does ACP stand for?
- In commerce, ACP stands for Agentic Commerce Protocol, the OpenAI and Stripe specification for agent-driven checkout. The same three letters have been used for unrelated agent-communication specifications elsewhere in the AI tooling world, so check who published the document you are reading before assuming it is the commerce one.
- Is ACP the same thing as agentic commerce?
- No. Agentic commerce is the activity — an AI agent performing discovery, comparison and purchase on a shopper's instructions. ACP is one specification covering part of that activity. Agents already buy from stores implementing no protocol at all, by reading structured product data, so the activity does not depend on the specification existing.
- How is ACP different from UCP?
- Sponsorship explains it. UCP comes from Google and Shopify, whose interest is agents reading merchant catalogs, so it specifies discovery and cart. ACP comes from OpenAI and Stripe, whose interest is a purchase completing inside an assistant, so it specifies checkout sessions and payment delegation. They overlap at the cart and share one requirement: live price and availability.
- Do I need ACP to sell to AI agents?
- No. Assistants read structured product data from ordinary storefronts today with no protocol involved. ACP matters when the purchase is meant to complete inside the assistant rather than on your site. The feed work it requires is shared with every other standard in the space and pays back regardless; the checkout half is the part that is a bet.
- Does ACP make the AI agent the merchant of record?
- No. Payment delegation is designed the other way around: the agent environment hands processing to the merchant's processor rather than holding credentials or settling itself. The merchant keeps the processor relationship, the settlement and the customer record — and, correspondingly, the chargeback liability.
In depth: What is ACP? A merchant guide