Why Protocols Matter
In traditional e-commerce, a human navigates to a website, browses products, and checks out through the merchant's own payment page. The entire transaction happens within systems designed for people.
Agentic commerce breaks that model. When an AI agent initiates a purchase, it needs a structured way to communicate with the merchant's systems: requesting product information, building a cart, handling payment credentials securely, and confirming the order. Without a shared standard, every AI platform would need a bespoke integration with every merchant, creating an unworkable complexity.
Protocols solve this. They create a common language so that a single integration allows a merchant to sell through any compatible AI agent.
How ACP Works
ACP defines a set of REST API endpoints that merchants implement to make their checkout accessible to AI agents. The flow follows a clear sequence.
The buyer expresses intent through an AI interface, such as ChatGPT. The agent sends a checkout request to the merchant. The merchant returns the current state of the cart, including available payment methods, shipping options, and totals. The agent renders this to the buyer. Once the buyer confirms, the agent provisions a Shared Payment Token, a new payment primitive from Stripe that allows the AI platform to initiate payment without exposing the buyer's actual payment credentials. The token is scoped to that specific merchant and cart total. The merchant processes the payment through their existing provider and confirms the order.
Throughout this process, the merchant remains the merchant of record. They retain control over what products are sold, how they are presented, and how orders are fulfilled. The AI agent acts as an intermediary, not a marketplace.
ACP and UCP: Two Standards, One Direction
In January 2026, Google released the Universal Commerce Protocol at the National Retail Federation conference. UCP takes a broader scope than ACP, covering the full commerce journey from product discovery through to post-purchase support including returns and order tracking.
UCP was co-developed with Shopify, Etsy, Wayfair, Target, and Walmart, and endorsed by over 20 partners including Visa, Mastercard, American Express, Adyen, and Stripe. It is designed to be interoperable with existing protocols including ACP, Agent2Agent (A2A), Agent Payments Protocol (AP2), and Model Context Protocol (MCP).
The two protocols are complementary rather than competing. ACP focuses on the checkout transaction. UCP standardises the full lifecycle. Both are open source and both aim to prevent the same problem: merchants having to build separate integrations for every AI agent that wants to sell their products.
The Compliance Gap
Both ACP and UCP address the mechanics of transactions, but the question of identity and compliance sits alongside them. When an agent acts on behalf of a person, someone needs to prove that the action was authorised. Both protocols include payment security through tokenisation and scoped permissions, but the broader questions of agent identity, delegation authority, and regulatory compliance require additional infrastructure.
This is the layer where compliance providers operate. Proving who authorised an agent action, what limits applied, and whether the transaction was permissible under applicable regulations requires identity verification, delegation credentials, and audit-grade evidence. As Visa, Mastercard, and others have noted, these capabilities will be foundational to agentic commerce scaling safely.
Frequently Asked Questions
What is the Agentic Commerce Protocol?
The Agentic Commerce Protocol (ACP) is an open standard created by OpenAI and Stripe that defines how AI agents and merchants communicate to complete purchases. It includes specifications for checkout, payment handling, and order confirmation, and is open-sourced under the Apache 2.0 licence.
What is the difference between ACP and UCP?
ACP, developed by OpenAI and Stripe, focuses on the checkout transaction between an AI agent and a merchant. UCP, developed by Google with partners including Shopify and Walmart, covers the full commerce journey from discovery to post-purchase support. Both are open source and designed to be interoperable.
Can merchants use both ACP and UCP?
Yes. The protocols are designed to work alongside each other. Stripe is an endorsed partner of both standards. A merchant implementing UCP can also support ACP-compatible agents, and vice versa. The aim is interoperability, not exclusivity.
Who is already using ACP?
As of early 2026, ACP powers Instant Checkout in ChatGPT. US-based Etsy sellers were the first merchants, with over one million Shopify merchants including Glossier, SKIMS, Spanx, and Vuori announced as coming soon. Salesforce has also announced ACP integration for its Agentforce Commerce platform.
