ACP, UCP, AP2 and MCP Compared: What Each Agentic Commerce Protocol Does

MCP, ACP, UCP and AP2 do different jobs. MCP (Model Context Protocol) lets an AI agent use tools and read data. ACP, UCP and AP2 deal with checkout and payment: how an agent starts a purchase and how a buyer's approval is proven. They are not direct rivals, but ACP and UCP do overlap.

Why there are several protocols

A shopping agent has to do many different things. It must find products, read their data, ask for a price, start a checkout, and pay with the buyer's consent. No single protocol covers all of this.

So different companies have published different parts. Some parts overlap. This area changes fast, so treat this article as a map and read the current specification before you build anything.

The protocols in short

MCP: tool and data access

MCP was created by Anthropic. In December 2025 it was donated to the Linux Foundation's Agentic AI Foundation.

MCP defines how an AI application connects to a server that offers tools, data and prompts. A store could offer an MCP server with tools such as "search products" or "get order status". The agent calls these tools in a standard way.

MCP does not handle payment. It is a general way to connect agents to systems, not only for shopping.

ACP: Agentic Commerce Protocol

ACP comes from OpenAI and Stripe. It describes how an agent, such as an AI assistant, starts and completes a checkout with a merchant.

In the public description, the merchant stays the seller. The payment is passed on in a controlled way, so the agent does not handle raw card data. Read the specification for the exact token and API details.

UCP: Universal Commerce Protocol

UCP is a Google and Shopify effort. It aims to give agents one common way to talk to many merchants and platforms, from product discovery to checkout.

UCP and ACP both address agent checkout, so they overlap. Which one a store uses will mostly depend on the platform, the payment provider and the AI surfaces where the store wants to appear. Check the current status of both.

AP2: Agent Payments Protocol

AP2 comes from Google, together with payment networks and other partners. Its focus is trust in the payment itself.

The core idea is that a buyer's approval should be provable. AP2 uses signed records, called mandates, that show what the buyer allowed the agent to do. This helps later when someone asks, "Did the buyer really want this?"

A2A: Agent2Agent

A2A is a Google protocol for communication between agents. It is not a payment protocol. It matters when a shopping agent has to work with other agents, such as a merchant's own agent.

How the pieces fit together

A simple way to think about it is in layers:

• Data layer. Your product pages, structured data and feeds. Every agent needs this.
• Tool layer. MCP, for access to tools and live data.
• Agent-to-agent layer. A2A, where agents work with other agents.
• Checkout layer. ACP or UCP, to create and complete an order.
• Payment trust layer. AP2 and the payment provider's own tools, to prove consent and move money safely.

In real systems the lines blur. Some protocols reach into more than one layer. The layers still help you ask the right question: "What do I need for this step?"

What this means for a store owner

Most store owners will not implement these protocols directly. Your platform, your payment provider or a plugin vendor will do that work. Your job is to be ready on the inputs.

• Keep product data accurate and complete. Every protocol depends on it.
• Know which payment provider you use, and ask what it supports.
• Watch your platform's announcements. Shopify and WooCommerce differ here.
• Keep order, tax and invoice data clean. An order from an agent still needs a correct invoice.

A short checklist for choosing what to follow

1. Write down your platform and payment provider.
2. Search their official documentation for the words "agent", "MCP", "ACP" and "UCP".
3. If they support a protocol, follow their setup steps. Do not build your own version.
4. If they do not, improve your product data and structured data first.
5. Review the situation every quarter. The picture will change.

What is still open

Several questions have no settled answer yet.

• Which checkout protocol will be common in your market?
• How will refunds, disputes and liability work across agent, platform and merchant? Terms differ by provider.
• How will identity and consent be checked across borders?
• How will data protection rules apply to data that agents collect?

For legal questions, read the official texts and ask a qualified adviser.

Frequently asked questions

Is MCP a payment protocol?

No. MCP gives agents access to tools and data. A checkout can be one of those tools, but the payment itself is handled by checkout and payment protocols and by your payment provider.

Do ACP and UCP replace each other?

Not at the moment. Both address agent checkout, and they come from different companies. A merchant may support one, both or neither, depending on platform and provider.

What is a mandate in AP2?

A mandate is a signed record of what the buyer allowed the agent to do, such as a spending limit or a specific cart. It gives the merchant and the payment provider proof of consent.

Which protocol should a small store learn first?

None of them in detail. Start with product data and structured data, then follow what your platform and payment provider announce. They will tell you which protocol to use.