ACP, UCP, AP2 and MCP: Agentic Commerce Protocols Explained

If you have read three articles on agentic commerce, you have met four acronyms and probably decided they were the same thing. They are not. Each one does a different job, and knowing which job is the fastest way to decide what your store actually has to do.

The four, in one table

Dates and roles are from Wikipedia’s agentic commerce entry, OpenAI and Stripe for ACP, and NRF and Google for UCP. Both ACP and UCP were released under the Apache 2.0 license.

How they fit together

They stack more than they compete. A shopper’s agent uses ACP or UCP to find products and complete checkout with a merchant. AP2 or a card network’s agent credentials prove the person allowed the purchase. MCP sits beside them, as the way an agent calls tools such as your catalog or order system. Under all of it are your own systems.

Plate 1 · The agentic commerce stackWho defines what

The ACP design is a good example of the stack at work. The agent collects the buyer’s payment choice and hands the merchant a narrowly scoped token. The merchant charges that token through any compliant payment provider and stays the merchant of record.

Plate 2 · How it arrivedThree announcements in four months

What is live and what is early

ACP went live with Etsy on launch day, and a dozen Shopify brands including Glossier, Vuori, Spanx and SKIMS followed over the next weeks. For merchants already on Stripe, the companies said enabling agentic payments could take as little as one line of code, and merchants on other processors can take part through Stripe’s Shared Payment Token API or the Delegated Payments Spec.

UCP is newer. At launch its checkout experience was limited to eligible products in the United States and participating merchants, on surfaces such as AI Mode in Google Search and the Gemini app. Check current availability before you plan around it, because these programs are moving quickly.

Do you have to pick one?

Probably not, and not yet. Which protocol your store ends up using will largely depend on your commerce platform and payment provider, not on a technical preference. Shopify co-developed UCP, and Stripe co-developed ACP. If you run a custom stack, the specifications are open, so you can implement against them once your data is ready.

The work that helps under every protocol is the same, and it is not protocol work:

1. Fix your product data. Identifiers, variants, literal attributes and a single source of truth. The 12-point audit covers it.
2. Make price and stock real-time so what an agent quotes is what you charge.
3. Publish policies in a form a machine can read, especially returns and shipping.
4. Check your platform’s program. Look in your commerce platform and payment provider for current agentic commerce options before building anything.
5. Test what an agent says about you. Ask real shopper questions and read the answers. Here is a method.

Which situation are you in?

What is still unsettled

Everything here is under two years old. Programs are limited by region and merchant eligibility, field requirements change, and fees and liability terms are still being worked out. We are not lawyers, and this is not legal advice. Read each platform’s current terms before you commit.

Common questions

Is ACP the same as MCP?

No. ACP defines how an AI agent gets product data, builds a cart and checks out with a merchant. MCP is a general way for an agent to call tools and data sources. It does not define merchant checkout flows.

Which protocol should my store support first?

Start with product data and real-time price and stock, which every protocol needs. Then follow your commerce platform and payment provider. Stripe merchants have an ACP path, and Shopify co-developed UCP.

Does the AI agent become the merchant of record?

Under ACP, the merchant stays the merchant of record. The agent hands over a narrowly scoped payment token and the merchant charges it through a compliant payment provider.

Do these protocols replace my website?

No. Agents still need accurate product data, and shoppers still land on your site for many purchases. The protocols add another route to the sale.

Are ACP and UCP open?

Yes. Both were released under the Apache 2.0 license.