Agentic commerce protocols are open specifications that let AI agents discover products, check out and pay on a buyer’s behalf. The Agentic Commerce Protocol (ACP) from OpenAI and Stripe covers checkout. The Universal Commerce Protocol (UCP), governed by Google, Shopify and others, covers catalogue to order. Google’s Agent Payments Protocol (AP2) proves a buyer authorised a payment. The Model Context Protocol (MCP) connects agents to tools in general. Most businesses reach them through their commerce or payments platform rather than building them directly.
Why there is more than one protocol
An agent buying something has to do several jobs: find the product, understand the options, build a cart, check out, pay and confirm the order. Each protocol standardises a different part of that journey, so they overlap less than the names suggest.
All four protocols below are published openly. ACP, UCP and AP2 are licensed under Apache 2.0, and MCP describes itself as an open-source standard.
The protocols at a glance
This summary is based on each protocol’s own documentation, linked in the sources below.
| Protocol | Maintained by | What it covers | First release |
|---|---|---|---|
| Agentic Commerce Protocol (ACP) | OpenAI and Stripe | Checkout between buyer, agent and seller, including passing payment credentials | Specification released 29 September 2025 |
| Universal Commerce Protocol (UCP) | Governing council with Google and Shopify as permanent members; Stripe joined in April 2026 | Catalogue, cart, checkout, identity linking and orders | Protocol release dated 11 January 2026 |
| Agent Payments Protocol (AP2) | Google, with industry collaborators | Proof that the buyer authorised a purchase, using signed mandates | Announced September 2025 |
| Model Context Protocol (MCP) | Open-source project | A general way to connect AI applications to external tools and data | Not commerce-specific |
Agentic Commerce Protocol (ACP)
ACP describes itself as an open specification for a programmatic exchange between buyers, their AI agents and sellers to complete a purchase. It was developed by Stripe and OpenAI, and OpenAI was the first platform to implement it in ChatGPT.
The seller stays the merchant of record: the agent starts the checkout and passes a payment credential, and the seller processes the order. Stripe’s Shared Payment Token is one way to pass that credential. ACP also states that it is compatible with both REST and MCP.
Universal Commerce Protocol (UCP)
UCP aims to provide building blocks for agentic commerce from discovery to checkout and beyond. Its documentation covers catalogue, cart, checkout, identity linking and orders. Google uses it for direct buying in AI Mode and the Gemini app.
UCP is run by a governing council whose permanent members are Google and Shopify. Its site lists retailers and platforms including Etsy, Wayfair, Target and Walmart among co-developers. Stripe is a member and offers a payment handler for UCP checkouts.
Agent Payments Protocol (AP2)
AP2 deals with a narrower question: how a merchant or payment provider knows the buyer really asked the agent to make this purchase. It uses signed mandates to record intent, the cart and the payment, for purchases where the buyer is present and for ones made on their behalf later.
Google announced AP2 in September 2025 with more than 60 collaborators across payments and commerce. It is designed to work alongside checkout protocols rather than replace them.
Where MCP fits
MCP is not a commerce protocol. It is a general standard for connecting AI applications to external systems, which is why it appears in so many agent integrations. A business can use MCP to let agents use its product or service directly, and commerce protocols can be offered through it.
Which protocols does a business need?
Most merchants do not implement these protocols themselves. Commerce platforms and payment providers increasingly support them on the merchant’s behalf: Shopify through its AI channels and Stripe through its Agentic Commerce Suite, for example. The practical job is to check which channels your platform supports and whether you are eligible.
Protocol support does not make an agent choose you. An agent still needs accurate product facts, clear policies and a checkout that works for the exact item and variant. Test that journey before and after connecting a new channel.
- Ask your commerce platform and payment provider which protocols and AI channels they support for your store
- Check eligibility by country, currency and product type before promising availability
- Make product facts, variants, prices and policies explicit and consistent across your site and feeds
- Test discovery, cart and checkout through each channel you enable
- Record agent-led orders separately so you can measure the channel
Related guides
Read the underlying announcements and guidance
Questions about agentic commerce protocols
What is the difference between ACP and UCP?
ACP, from OpenAI and Stripe, focuses on checkout between a buyer’s agent and a seller. UCP, governed by Google, Shopify and others, covers a wider journey from catalogue to order. A business may be reachable through both via its platform.
Is AP2 a competitor to ACP?
Not directly. AP2 focuses on proving a buyer authorised a payment, and is designed to work alongside checkout protocols.
Do I need to build an agentic commerce protocol integration?
Usually not. If you sell through a major commerce or payments platform, start by checking what it already supports. Custom integrations make sense mainly for platforms and large merchants.
Is MCP an agentic commerce protocol?
No. MCP is a general standard for connecting AI applications to tools and data. It is often used to expose commerce functions to agents.