ACP Explained: The Agentic Commerce Protocol

The Agentic Commerce Protocol (ACP) is an open standard for letting an AI agent complete a purchase with a merchant. Its purpose is narrow and practical: give agents and stores a shared language for checkout so a merchant builds one integration instead of a different one for every AI platform.

Who is behind it

ACP was launched on 29 September 2025 by OpenAI and Stripe, and it powered the original “buy it in ChatGPT” Instant Checkout experience. The project’s README describes OpenAI and Stripe as the founding maintainers that jointly govern the project, while MAINTAINERS.md lists OpenAI, Stripe, and Meta as lead maintainers. Stripe’s own ACP documentation now also describes the standard as created by Stripe, OpenAI, and Meta, which is the clearest first-party confirmation of Meta’s role. Meta is also a member of the rival UCP Tech Council, so it remains tied to both commerce-layer efforts. ACP is licensed under Apache 2.0, requires a contributor license agreement, and is governed through a public proposal process, with a stated future path of “neutral foundation stewardship as ecosystem matures.”

What ACP actually does

ACP standardizes the checkout conversation between a buyer’s agent and a merchant. The specification covers agentic checkout (creating, updating, and completing a checkout session), cart and product feed, delegated payment, delegated authentication via OAuth 2.0, and orders and webhooks for confirmation, shipping, delivery, and refunds.

Crucially, the merchant stays in control. They remain the merchant of record and keep the customer relationship, fulfillment, returns, tax, and support. ACP is the handshake at the checkout, not a takeover of the store.

It is just as important to be clear about what ACP is not. It is not a tool-discovery protocol, that job belongs to MCP. It is not an agent-identity or attestation layer. And it is not a crypto-settlement protocol. ACP describes itself as compatible with both plain REST and MCP, and it deliberately leaves those adjacent layers to other standards.

How payment flows

This is the part most people get wrong, so it is worth being precise. When a buyer checks out, the payment service provider (Stripe in the reference implementation) issues a Shared Payment Token: a single-use credential that is scoped to one specific merchant and one specific cart total. The agent, for example ChatGPT, passes that token to the merchant through the ACP interface, and the merchant charges it through their own processor.

The point of the design is that the agent never sees the buyer’s actual card details, and the token cannot be reused for a different amount or a different merchant. Merchants already on Stripe can enable it with minimal code; merchants on other processors can adopt it through the Shared Payment Token API or the protocol’s Delegated Payments specification.

1. 1BuyerPay

   The buyer pays through the inline checkout.

2. 2ProviderTokenize

   The payment provider issues a token, scoped to one merchant and one total.

3. 3AgentHand off

   The agent passes the token on, never the card.

4. 4MerchantCharge

   The merchant charges it; the token cannot be reused.

What is actually live

Here the gap between announcement and reality matters, and it is the single most misreported part of ACP’s story.

Etsy was genuinely live from day one for US buyers. Walmart announced a partnership with OpenAI on 14 October 2025 under which customers and Sam’s Club members would “soon” be able to shop Walmart through ChatGPT using Instant Checkout. PayPal announced on 28 October 2025 that it would adopt ACP to bring its merchant network into ChatGPT, using the delegated payments API. Note that both were announcements of intent, not confirmations of a live integration.

The widely repeated claim that “over a million Shopify merchants” went live is not accurate. Both OpenAI’s and Stripe’s launch announcements described those merchants as “coming soon,” and only a small number of Shopify merchants actually integrated. In March 2026 OpenAI told trade press that “Instant Checkout is moving to Apps” and that it was prioritizing search and product discovery, “with the Agentic Commerce Protocol serving as the infrastructure.” In practice that repositions the in-chat “buy now” moment toward ChatGPT Apps and toward discovery that sends shoppers to a merchant’s own checkout. The protocol itself continues as the connective infrastructure, but the flagship “buy directly inside the chat” experience was pulled back. The lesson is that adoption of a standard depends as much on the host surface promoting it as on the standard itself.

The specification is officially in beta. ACP uses date-based versioning, and the latest stable version is 2026-04-17. The released versions to date are 2025-09-29 (initial release), 2025-12-12 (fulfillment enhancements), 2026-01-16 (capability negotiation), 2026-01-30 (extensions, discounts, payment handlers), and 2026-04-17 (cart, feed, orders, authentication, and MCP), with current work staged in an unreleased directory. Note that ACP’s own documentation site has not always kept pace with the repository, so the spec/ directory on GitHub is the authoritative record of what is current.

Where it sits in the wider landscape

ACP is the checkout layer. Around it sit several other standards that mostly compose with it rather than replace it: AP2 handles payment authorization and trust, MCP handles discovery, and x402 handles machine-native stablecoin settlement. The one genuine rival at the commerce-semantics layer is Google’s Universal Commerce Protocol (UCP), launched in January 2026 with backers including Shopify, Etsy, Target, Wayfair, and Walmart, which aims at the broader shopping journey rather than checkout alone. In April 2026 its Tech Council doubled to ten members as Amazon, Meta, Microsoft, Salesforce, and Stripe joined, and on 28 April 2026 Stripe also joined UCP’s Governing Council alongside permanent members Google and Shopify. So Stripe now co-maintains ACP and sits on both of UCP’s governing bodies, and Meta is a lead maintainer of ACP and a member of the UCP Tech Council. That is a clear sign the standards are still settling and that the largest players are hedging rather than picking a side. For a side-by-side, see ACP vs UCP; for the full map, see the protocol stack.

What it means for you

If you are a merchant, ACP is one of the two checkout-layer standards worth tracking, alongside UCP. Adopting it is what makes your products buyable from an agent surface that supports it; for a step-by-step integration, see how to implement ACP. If you are a builder, treat ACP as the checkout handshake and pair it with a discovery layer and a payment-authorization layer rather than expecting it to do everything. And whatever you read about adoption numbers, check whether a partner is actually live or merely announced.

FAQ

Who maintains ACP? ACP’s README describes OpenAI and Stripe as founding maintainers, while MAINTAINERS.md lists OpenAI, Stripe, and Meta as lead maintainers. Meta also sits on the rival UCP Tech Council. It is Apache 2.0 licensed.

Did a million Shopify merchants go live on ACP? No. Both launch announcements described those merchants as “coming soon,” not live. Only a handful integrated, and in March 2026 OpenAI said Instant Checkout was moving to Apps, with ACP serving as the underlying infrastructure. Etsy was genuinely live from launch.

How does payment work without sharing card details? A Shared Payment Token, scoped to one merchant and one cart total, is issued and passed to the merchant. The agent never touches the raw card credentials.