Agentic Commerce Protocol (ACP)

The Agentic Commerce Protocol (ACP) is an open standard developed by OpenAI and Stripe. It defines how AI agents — such as ChatGPT — can find products, assemble shopping carts, and securely complete purchases without the user leaving the chat interface.

While traditional e-commerce was built for human users in browsers — with product pages, shopping carts, and checkout forms — ACP creates a machine-readable interface through which AI agents can programmatically handle the entire purchase process. The protocol is part of a larger movement toward Agentic Commerce: a commerce model in which autonomous AI agents shop on behalf of users.

Why Does ACP Exist?

Today's online commerce is optimized for human clicks. Every interaction — from browsing a category to entering a credit card number — assumes a human at the screen. When an AI agent needs to shop on behalf of its user, it faces a problem: there is no standardized way to communicate with online stores.

Without ACP, every integration between an AI agent and a merchant would require custom code. An agent that needs to shop at 100 stores would have to maintain 100 different integrations. That doesn't scale.

ACP solves this problem through standardization. A merchant implements the protocol once — and automatically becomes accessible to every ACP-compatible agent. The core promise is: "Build once, distribute to any agent."

The comparison is fitting: ACP is to Agentic Commerce what HTTP was to the web — a common protocol that standardizes information exchange between different systems.

Who Is Behind ACP?

OpenAI primarily initiated ACP and provides the first production implementation with ChatGPT. Through "Instant Checkout," ChatGPT users can purchase products directly in the chat — without being redirected to the merchant's browser.

Stripe provides the payment infrastructure. The new Agentic Commerce Suite enables Stripe customers to integrate with minimal effort: those already using Stripe can connect to ACP with minimal work. Stripe handles secure payment processing via tokenized credentials.

Governance of the protocol currently lies with the Founding Maintainers (OpenAI and Stripe), with an announced path toward broader community governance. The project is available on GitHub as an open-source repository and accepts contributions via RFCs (Request for Comments).

The Three Building Blocks of ACP

ACP is structured in three layers, each standardizing a different part of the purchase process:

1. Product Feed Spec

Merchants provide their product data in a standardized, machine-readable format. The feed contains all the information an AI agent needs to make meaningful recommendations:

• Product details: Name, description, images, variants (size, color)
• Prices and availability: Current price, inventory, shipping options
• Searchability: Categories, tags, attributes for filtering
• Checkout capability: Which products can be purchased directly via ACP

Instead of an agent having to scrape a merchant's website — an error-prone and fragile process — the Product Feed provides a clean, structured data source.

2. Checkout API

The Checkout API is the heart of ACP. It defines a REST-based interface with four endpoints:

• CreateCheckout: The agent creates a new checkout session with the merchant. Contains the selected products, quantities, and optionally the shipping address.
• UpdateCheckout: Changes to the cart — such as quantity changes, coupon codes, or shipping options.
• CompleteCheckout: The agent completes the purchase, including payment information.
• CancelCheckout: Cancellation of the transaction.

Crucially: the merchant retains full control. Prices, shipping costs, taxes, and order logic are calculated server-side by the merchant — not by the agent. The agent only displays what the merchant's backend returns. More on the technical details on the Checkout API page.

3. Delegated Payment

For secure payment processing, ACP uses SharedPaymentTokens — tokenized payment information that the agent forwards to the merchant on behalf of the user. The process:

• The user stores their payment method once with the agent (e.g., in ChatGPT)
• During a purchase, the agent generates a temporary token
• The merchant receives the token and processes the payment through their existing payment stack
• The actual card data is never transmitted in plain text to the agent or the merchant

How Does a Purchase via ACP Work?

A concrete flow, step by step:

1. User expresses purchase intent: "I need new running shoes, max 120 euros, neutral cushioning."
2. Agent searches Product Feeds: The AI agent queries product data from multiple ACP-compatible merchants and filters by the user's criteria.
3. Agent presents options: "I found three matching models: [Product A, B, C with prices and images]."
4. User selects: "Take Product B in size 43."
5. Agent creates checkout session: Via CreateCheckout, a cart is created with the merchant.
6. Merchant calculates details: Shipping costs, taxes, estimated delivery time — all determined by the merchant's backend.
7. Agent shows summary: "Product B, size 43, EUR 109.95 + EUR 4.95 shipping. Delivery in 2-3 business days."
8. User confirms: "Yes, buy it."
9. Agent provisions SharedPaymentToken: The tokenized payment information is created.
10. Agent sends CompleteCheckout: The checkout session is completed with the payment token.
11. Merchant processes payment: The transaction is processed through their payment provider (e.g., Stripe).
12. Confirmation: "Ordered! Order number #12345. You'll receive an email from the merchant."

The entire process takes place in the chat. The user neither needs to visit a website nor fill out a checkout form.

Current Implementations

ACP is not a theoretical concept — it is already being used in production:

• ChatGPT Instant Checkout: The first implementation. Users in the USA can purchase directly in ChatGPT. Initial partners include Etsy, among others.
• Stripe Agentic Commerce Suite: A toolkit for merchants that enables ACP integration via existing Stripe accounts. The fastest way for Stripe customers to become ACP-compatible.
• Shopify: Over 1 million merchants are in the pipeline for native ACP support. Shopify additionally provides an MCP server that gives agents access to product catalogs and checkout.
• BigCommerce: Has announced a native ACP integration.

ACP can be implemented both as a classic REST API and as an MCP server — merchants can choose which integration path best fits their infrastructure.

ACP Compared to Other Protocols

ACP is not the only protocol for Agentic Commerce. In particular, the Universal Commerce Protocol (UCP) by Google and Shopify and the Agent Payments Protocol (AP2) by Google and Mastercard address similar problems — with different focuses.

• ACP vs. UCP: ACP concentrates on the moment of purchase — checkout and payment. UCP covers the entire commerce lifecycle: from product discovery through identity linking to post-purchase management (returns, tracking).
• ACP vs. AP2: ACP is checkout-centric; AP2 is a universal payment framework with "Mandates" — digitally signed authorizations that are not limited to shopping.
• Coexistence: The protocols are not mutually exclusive. A merchant could implement ACP for ChatGPT purchases and UCP for Google-based agents.

A detailed comparison can be found on the ACP vs. UCP vs. AP2 page.

Critical Assessment

Despite all the momentum, a sober assessment is warranted:

• Still beta, still US-only: The Instant Checkout in ChatGPT is limited to the USA. International expansion has been announced, but without a specific date for Europe.
• Stripe dependency: The Delegated Payment layer currently relies primarily on Stripe. Additional payment providers — including PayPal — have been announced as partners but are not yet integrated.
• Loss of customer contact: When customers buy through an AI agent instead of the merchant's website, the merchant loses valuable data: browsing behavior, cart analytics, upselling opportunities. The startup Forter has proposed the Trusted Agentic Commerce Protocol (TACP) as an answer, which forwards customer data to the merchant via JWE encryption.
• Regulatory questions: In Europe, GDPR (data processing by agents), PSD2 (Strong Customer Authentication for payments), and the AI Act must be considered. How ACP will meet these requirements remains open.

Outlook

ACP will continue to evolve. The most important expected developments:

• International expansion: Support for additional countries, currencies, and local payment methods (SEPA, iDEAL, Klarna).
• More complex carts: Multi-merchant carts — an agent purchases products from different merchants in a single transaction.
• Vertical extensions: Specialized protocol extensions for industries like automotive, B2B, or real estate that require more complex purchase processes.
• Multi-agent orchestration: Multiple specialized agents work together — one researches, one compares prices, one completes the purchase.

ACP Subpages