Agentic Commerce Protocol (ACP): What It Is and How It Works

The Agentic Commerce Protocol (ACP) is an open standard that defines the interaction model between a shopper, their AI agent, and a merchant so the agent can complete a purchase on the shopper's behalf. OpenAI and Stripe released ACP on September 29, 2025, and continue to maintain the specification under the Apache 2.0 license. Stripe described it at launch as a standard that "already powers the new Instant Checkout in ChatGPT." The protocol is currently in beta and uses date-based versioning, with the latest stable snapshot dated 2026-04-17.

ACP is one of several open standards shaping agentic commerce. Its narrow job is the checkout session: how the agent and the merchant exchange cart, payment, and order information securely while the merchant remains the system of record for the order, payments, taxes, and compliance. Product discovery and merchant onboarding are handled by each AI platform separately, not by the ACP specification itself.

Because ACP is an open standard, businesses can adopt it even if they do not process payments with Stripe. Stripe's implementation is the first compatible reference and OpenAI's implementation powers ChatGPT, but the specification is designed to be processor- and platform-flexible.

What ACP specifies today is the checkout session and the secure sharing of payment credentials among the shopper, agent, merchant, and payment provider. The reference specification covers checkout sessions, capability negotiation, payment handlers (including seller-backed payment handlers), extensions, and discounts. The 2026-04-17 release added cart, feed, orders, authentication, and Model Context Protocol (MCP) compatibility.

What ACP explicitly leaves out of scope are PSP authorization and capture semantics, returns and exchanges, tax configuration, and fraud modeling. Those stay with the merchant's payment service provider and commerce stack.

Product discovery is not specified by ACP. The official ACP site states that products do not appear automatically and that each AI platform manages its own onboarding, with discovery tooling still in progress. OpenAI publishes a separate commerce API and product feed format for getting a catalog indexed in ChatGPT; see ChatGPT Product Feed Format for that layer.

ACP defines four participants in a checkout:

• Shopper. The consumer who authorizes the purchase and owns the payment credentials.
• AI agent. The application, such as ChatGPT, that discovers, presents, and completes the purchase on the shopper's behalf. The agent is explicitly not the merchant of record.
• Merchant. The business that owns the product, the order, taxes, and compliance, and remains the system of record for the transaction.
• Payment provider. The merchant's payment service provider, which processes the payment. ACP passes secure payment tokens between the buyer and the business through the agent rather than exposing raw card details to the agent or the merchant.

The flow is a checkout-session lifecycle: the agent creates a checkout session, updates it as the shopper confirms selections, and completes it to create an order, or cancels it. Checkout can complete inside the agent interface, or the merchant can use a redirect mode that hands the shopper back to the merchant's site. Both are valid ACP paths; which one a shopper sees depends on the merchant's and platform's implementation, not on the protocol.

ACP itself is an open standard with no protocol-level fee. A merchant's costs come from the payment processor and commerce platform it already uses, not from ACP.

Stripe's first compatible implementation uses Stripe's standard payment processing and its Shared Payment Token, so merchants already on Stripe pay their existing Stripe processing rates. Because the specification is processor-flexible, merchants on other payment providers can adopt ACP through their own provider's implementation when one is available.

Be specific when comparing costs. Protocol fees (none for ACP), platform fees from an AI surface, and payment-processing fees from a PSP are three different things, and only the last two ever show up on a merchant's bill.

The only live consumer surface confirmed in primary sources is Instant Checkout in ChatGPT, with merchant onboarding handled by OpenAI through chatgpt.com/merchants. Stripe named its early agentic-commerce launch partners as AI agent platforms (Microsoft Copilot, Anthropic, Perplexity, Vercel, Lovable, Replit, and Manus), not consumer retailers.

ACP's own documentation states that products do not appear automatically and that discovery tooling is in progress, so treat any specific merchant-count or auto-enrollment claim with caution unless it comes from a current primary source. Product discovery in ChatGPT is managed by OpenAI's commerce API and feed, which is separate from the ACP checkout specification.

ACP supports configuring checkouts for physical goods, digital goods, subscriptions, and asynchronous purchases. The specification's fulfillment types include shipping and digital.

Current limitations are mostly about what is out of scope rather than what is unsupported: PSP authorization and capture semantics, returns and exchanges, tax configuration, and fraud modeling all remain with the merchant's existing systems. On the OpenAI commerce onboarding side, prohibited categories include adult content, age-restricted products such as alcohol and nicotine, gambling, harmful or dangerous materials, weapons, prescription-only medications, and unlicensed financial products.

ACP and UCP overlap on checkout but differ in scope: ACP is narrowly the checkout session, while UCP covers discovery through post-purchase. MCP sits underneath as the data-access layer. AP2 and A2A are companion standards for payment authorization and agent communication. See the ACP integration checklist for implementation planning.

Paz helps commerce teams prepare for ACP-related discovery with catalog and AI-readiness checks, catalog quality scoring, human-reviewed optimization proposals, and OpenAI Commerce product-feed distribution on Growth and Enterprise.

Teams can then monitor Shopping Visibility across ChatGPT, Google AI Mode, Perplexity, and Google AI Overviews. Checkout, payments, orders, and fulfillment remain with the merchant's commerce stack and payment provider.