Personal Agent Protocol, UCP, ACP, AP2 and MCP: what each one does Free & Pro

Five names come up when people talk about AI agents and shopping. They are not five answers to one question. Three of them are about selling through an agent, one is about proving a payment was authorised, and one is a general way of giving an AI model tools. This guide says what each is, from its own published documents, as of 12 October 2026. All of them are drafts or early versions, and all of them may change. Agent Adapt implements one of them, the Personal Agent Protocol, and is not affiliated with or endorsed by the authors of any of them.

The short version

Protocol	Published by	What it covers	Where the checkout happens
Personal Agent Protocol	Sierra and Meta, with launch partners; Draft 0.1 on 9 Oct 2026	How a person’s agent identifies itself to a business, how the person signs in and grants access, and how the business serves the agent through APIs, its website or its own AI agent	At the business. Payments are an open topic in the draft.
Universal Commerce Protocol (UCP)	Co-developed by Google, Shopify, Stripe and others	The shopping journey from discovery to post-purchase: catalogue, cart, identity linking, checkout, order management; payment through AP2	Inside the platform or agent that runs the checkout
Agentic Commerce Protocol (ACP)	Published on OpenAI’s developer site, for ChatGPT	Product feeds, agentic checkout and delegated payment	Inside ChatGPT
Agent Payments Protocol (AP2)	Google; donated to the FIDO Alliance	Cryptographic proof that a person authorised a specific purchase and payment (mandates)	Not a checkout. A layer under one.
Model Context Protocol (MCP)	An open project; current revision 2026-07-28	A general way for an AI application to call tools and read data	Not a commerce protocol

Personal Agent Protocol

The Personal Agent Protocol describes the relationship between a person, their agent and a business. The agent carries a published identity and signs its requests; the person signs in on the business’s own site and chooses what the agent may view or change; the business publishes a discovery file and decides which agents it serves and how. The business can expose an OpenAPI-described API, an MCP server, its website or its own AI agent, and the person’s agent uses whatever it understands.

What it does not do, by its own open-topics page, is define payments. Under Draft 0.1 an agent cannot pay; the person does. For a store that means the checkout, the payment methods and the customer relationship stay where they are.

It is the protocol for the case where the customer’s own assistant comes to your store. Published under Apache 2.0. See The Personal Agent Protocol, explained.

Universal Commerce Protocol

UCP calls itself "the common language for platforms, agents, and businesses". Its site lists Google, Shopify, Stripe, Etsy, Wayfair, Target, Walmart, Amazon, Microsoft, Meta and Salesforce as co-developers of the shopping specification, with separate specifications in progress for lodging and food ordering. It covers catalogue search and lookup, building a cart, linking identities, checkout and managing orders, and it uses AP2 for payment. Apache 2.0.

The model is that a platform or agent runs the whole journey, including checkout, against a business that has implemented the protocol. The business is a supplier to that journey.

Agentic Commerce Protocol

ACP is published on OpenAI’s developer site, described there as a way to "build commerce flows for ChatGPT, including agentic checkout, delegated payment, and product feeds". A merchant supplies a product feed, implements a checkout specification, and accepts a delegated payment through a payment provider. The sale happens inside ChatGPT.

The site does not state a version number or a licence, and does not name its publishers beyond hosting the documents.

Agent Payments Protocol

AP2 answers a narrower question: when an agent makes a payment, how does everyone know the person really authorised that purchase? It uses signed, tamper-evident credentials called mandates. A Checkout Mandate records what was agreed with the merchant; a Payment Mandate authorises a payment against a particular instrument. Chained together they give an audit trail for both human-present and human-not-present payments.

Google published it and has donated it to the FIDO Alliance, where standardisation continues. It is designed to sit under a commerce protocol such as UCP rather than replace one. Apache 2.0.

Model Context Protocol

MCP is an open protocol for connecting AI applications to tools and data. It uses JSON-RPC messages between a host application, its clients and servers that provide tools, resources and prompts. The current specification revision is 2026-07-28. It is not about commerce; it is about giving a model the means to act.

It matters here because the Personal Agent Protocol lists MCP as one of the two API types a business may offer, and because many assistants can connect to an MCP server directly. Agent Adapt Pro runs one at your store. See Do you need an MCP server for your WooCommerce store?.

How they fit together

Think of two models of agent shopping.

In the platform-checkout model (UCP, ACP), the agent belongs to a platform, your products appear inside it, and the platform runs the checkout. AP2 can prove the payment was authorised. You gain reach inside that platform and give up the checkout.

In the your-store model (Personal Agent Protocol), the agent belongs to the customer and comes to you. You verify it, the customer approves it on your site, and it shops through your API and pays through your checkout. You keep the checkout and the relationship; you gain nothing you have not earned from the customer already.

A store can do both. They do not conflict, because they do not compete for the same checkout. MCP is a transport either model can use.

Which does a WooCommerce store need?

If customers’ own assistants are to work with your store, the Personal Agent Protocol is the one that describes that, and Agent Adapt is a plugin that implements it. If you want your products sold inside a particular platform’s assistant, you need that platform’s own programme and its feed, which is a separate decision and not something Agent Adapt does.

Common questions

Are any of these final?

No. The Personal Agent Protocol is Draft 0.1 and says it may change incompatibly. UCP publishes dated revisions. AP2 is at an early version under FIDO. ACP’s site gives no version. Treat every description above as true on 12 October 2026 and check the source before deciding anything expensive.

Does Agent Adapt implement UCP or ACP?

No. It implements the Personal Agent Protocol, Draft 0.1, with an MCP server in Pro. It does not generate product feeds for any platform.

Is the Personal Agent Protocol a competitor to UCP?

They overlap in subject but not in model. UCP’s checkout belongs to the platform running it; the Personal Agent Protocol’s draft leaves payments to the business and states payments as an open topic. Whether the two converge is for their authors to decide.

Where do I read the originals?

personalagentprotocol.org, ucp.dev, developers.openai.com/commerce, ap2-protocol.org and modelcontextprotocol.io. If something on this page is out of date, email [email protected] and we will fix it.