The short version
ACP and UCP are the two commerce protocols: each describes how an agent gets from a product to an order at a store. MCP is the general connection standard both can run over. AP2 handles payment authorisation, and A2A lets agents talk to each other. All of them read the same thing first: your product data.
| Protocol | Who is behind it | What it covers | Where it runs in 2026 |
|---|---|---|---|
| ACP Agentic Commerce Protocol | Stripe and OpenAI, open source under Apache 2.0 | Product feed, checkout API at the merchant, delegated payment token | ChatGPT reads the product feeds. Its in-chat checkout ended in March 2026. |
| UCP Universal Commerce Protocol | Google, Shopify and other companies, Apache 2.0 | Catalog, cart, checkout, identity linking and order, negotiated per store | Buying in AI Mode in Google Search and Gemini, opened to merchants through a waitlist |
| MCP Model Context Protocol | An open standard used by ChatGPT, Claude and others | How an assistant connects to tools and data. Not specific to commerce. | Apps in ChatGPT and connectors in Claude; in beta in WooCommerce |
| AP2 Agent Payments Protocol | Started by Google | Payment mandates: proof that the shopper authorised a purchase | Built into UCP as an extension |
| A2A Agent2Agent | Started by Google | Agents exchanging tasks with other agents | One of the transports UCP supports |
ACP: the Agentic Commerce Protocol
ACP was developed by Stripe and OpenAI and is published as open source under the Apache 2.0 license. ChatGPT was the first assistant to implement it, and Stripe the first payment provider, with its Shared Payment Token (agenticcommerce.dev).
It has three parts. A product feed tells the assistant what you sell. A checkout API, which the merchant implements, lets the assistant create, update, complete and cancel a checkout session. A delegated payment step gives the merchant a one-time token, limited to a maximum amount and an expiry, to charge through its own payment provider. The store stays the merchant of record.
What matters today is the feed. OpenAI wound down ChatGPT’s in-chat Instant Checkout in March 2026, and ChatGPT now sends the shopper to the merchant to buy. The full walkthrough, with the endpoints and a diagram, is in the Agentic Commerce Protocol, explained.
UCP: the Universal Commerce Protocol
UCP is built by Google together with Shopify and other retail, travel and payment companies, also under Apache 2.0 (ucp.dev). Where ACP defines one fixed checkout API, UCP works by negotiation:
- A profile at a fixed address. The store publishes a document at
/.well-known/ucpthat lists its services, its capabilities and the payment handlers it accepts. - Capabilities instead of one flow. Catalog, cart, checkout, identity linking and order are separate capabilities, with extensions such as fulfilment and discounts. Agent and store use the ones both support, in the newest version both list.
- Several transports. The same capability can be called over REST, MCP, A2A or an embedded checkout.
- Payment handlers. The store names the payment methods it accepts, and AP2 mandates can prove the shopper’s consent.
Google uses UCP for buying in AI Mode in Search and in Gemini. Merchants work from their existing Merchant Center feeds, join through a waitlist and remain the merchant of record (Google for Developers).
MCP: the Model Context Protocol
MCP is not a commerce protocol. It is the general standard an assistant uses to connect to tools and data, and it is how a store appears as its own app in ChatGPT or as a connector in Claude. A store offers a few tools, for example search, product details and cart, and the assistant calls them during the conversation.
Commerce protocols build on it: UCP lists MCP as one of its transports, and ACP can be published through an API or through MCP. WooCommerce ships an MCP integration in beta, from version 10.9, that lets assistants read a store’s products and orders (WooCommerce).
AP2 and A2A, briefly
AP2, the Agent Payments Protocol, deals with one question: how does a merchant know the shopper really authorised this purchase when an agent placed it? Its answer is a signed payment mandate. In UCP it is an extension, used when an agent buys on its own.
A2A, Agent2Agent, lets one agent hand a task to another, for example a shopping agent to a store’s agent. It is one of UCP’s transports. For a store owner, neither needs a decision today.
Which one does your store need?
| Your store runs on | ACP | UCP | MCP |
|---|---|---|---|
| Shopify | You do not implement either yourself. Shopify’s agentic storefronts connect eligible stores to ChatGPT, Google and Copilot, active by default. Agentic commerce for Shopify | Your own app in ChatGPT and Claude is a separate step. | |
| WooCommerce | Announced as coming soon, through Stripe | Announced as coming soon | In beta in WooCommerce 10.9. Agentic commerce for WooCommerce |
| Another platform | Start with product feeds for Google Merchant Center and for ChatGPT. They work today and every protocol reads them. | ||
The order of work is the same everywhere. First the catalog: brands, identifiers, clear descriptions, live prices and stock. Then the feeds. Then the connection, which is the part the protocols are still settling.
Where AgenticCart fits
AgenticCart covers the parts that work today, for WooCommerce and Shopify stores:
- Feeds. A feed in OpenAI’s format for ChatGPT shopping and a Google feed for Google Shopping, AI Mode and Gemini, built from your prepared catalog and kept up to date. See the ChatGPT product feed guide.
- Your own app over MCP. Your store as its own app in ChatGPT and Claude, on your domain and under your name: it searches your catalog, shows products, answers policy questions and builds a cart.
- The purchase in your checkout. AgenticCart does not take payments inside an assistant. The shopper gets a filled cart and pays in your store.
You can test what agents can read today with the free store check and grade a feed with the ChatGPT feed checker.
Frequently asked questions
What are agentic commerce protocols?
Shared rules that let an AI agent read a store's catalog, build a cart and place or prepare an order in the same way at every store. The main ones are ACP (Stripe and OpenAI), UCP (Google, Shopify and others) and MCP (the general standard for connecting assistants to tools). AP2 covers payment authorisation and A2A covers agents talking to each other.
What is the difference between ACP and UCP?
ACP was developed by Stripe and OpenAI and was first implemented in ChatGPT. It consists of a product feed, a checkout API the merchant implements, and a delegated payment token. UCP is built by Google, Shopify and other companies. A store publishes a profile at /.well-known/ucp, and agents negotiate capabilities such as catalog, cart, checkout and order with it. Both keep the store as merchant of record.
Is MCP a commerce protocol?
No. MCP, the Model Context Protocol, is a general standard for connecting AI assistants to tools and data. Commerce uses it as a transport: a store can offer search, product details and a cart as MCP tools, and both ACP and UCP can run over MCP.
Which protocol does my store need?
Start with product data and feeds, because every protocol reads them. On Shopify you do not implement them yourself: Shopify's agentic storefronts connect eligible stores to the assistants. On WooCommerce, MCP is in beta in WooCommerce itself, and ACP and UCP are announced as coming soon. A product feed for Google and for ChatGPT works on any platform today.
Do I have to choose one protocol?
No. They cover different assistants and overlap only in part, and all of them depend on the same thing: a clean, complete, machine-readable catalog. That work pays into every protocol at once.
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