Agentic Commerce Protocol (ACP) – OpenAI's protocol for AI-driven commerce

Definition

The Agentic Commerce Protocol (ACP) is a protocol initiated by OpenAI that lets AI agents carry out commercial actions, such as purchases and bookings, on a user's behalf.

What is the Agentic Commerce Protocol?

The Agentic Commerce Protocol, or ACP, is an OpenAI initiative that aims to let people buy directly through AI agents. Instead of the user browsing, comparing and completing a purchase themselves, ACP is built for a model where an AI agent acts as an intermediary and carries out actions on the user's behalf, within set limits.

ACP is about execution rather than visibility: how AI agents identify the right action, authenticate themselves, make decisions based on the user's instructions and complete transactions securely and traceably. Permissions, approval, payment and responsibility are the central questions.

For businesses, ACP marks a shift from simply presenting information to LLMs to enabling action. An offer that an AI agent is going to use has to be clearly defined, machine-readable and workable in practice – otherwise the agent cannot take the next step.

In practice, ACP complements other initiatives in AI-driven commerce, such as UCP. UCP deals with how commercial information is exposed to and understood by AI systems; ACP deals with how an agent carries out the action itself. Together, they point to a future in which AI does not just recommend – it also acts.

ACP vs UCP – two protocols with different scope

ACP was launched in September 2025 by OpenAI and Stripe, licensed under Apache 2.0, and powered ChatGPT's Instant Checkout feature until OpenAI changed course in March 2026: the purchase now happens in the merchants' own checkouts, while ChatGPT focuses on finding products and merchants can build their own apps in ChatGPT, according to CNBC. Google's Universal Commerce Protocol (UCP) was launched four months later, in January 2026 at NRF Retail's Big Show, and has a broader scope: the whole shopping journey from discovery to after-sales support, not just the payment step.

The main differences lie in where each protocol operates and in its design philosophy:

• ACP is optimised for a single agent – ChatGPT – and is closely tied to Stripe's payment solution. The checkout experience is polished, but discovery happens centrally via OpenAI's onboarding process.
• UCP is platform-agnostic and built for a multi-agent future. It can use REST, MCP or A2A as the transport layer and lets agents discover for themselves what a seller can offer via /.well-known/ucp endpoints.

In short: ACP is a polished checkout in a single shop. UCP is a high street where every shop can open a window onto any shopping agent.

How ACP works technically

ACP defines a structured conversational flow between buyer, AI agent and merchant. The protocol covers four essential layers:

• Intent & Reasoning – The LLM interprets the user's intent and formulates structured requests.
• Discovery – The agent uses MCP (Model Context Protocol) to fetch product data, stock levels and prices from the merchant's system.
• Transaction – Once a product has been chosen, ACP's checkout is called with time-limited, single-use payment tokens that give the user control and the merchant security.
• Fulfillment & Logging – Every step of the transaction is logged as the protocol specifies, so the flow can be audited and traced.

The merchant remains the "merchant of record" and keeps its customer relationship. The transaction runs through the merchant's own existing payment solution, just as in ordinary e-commerce, but an AI agent initiates it.

What it means if you sell products or services

For most businesses, ACP and UCP lead to the same strategic conclusion: visibility is no longer enough. Having your products mentioned in an AI answer is not sufficient – from now on, they also need to be purchasable through the agent, built on accurate, machine-readable product data.

According to OpenAI, ChatGPT handles over 50 million shopping-related questions a day. That makes it one of the largest AI-native commerce channels in existence – and a reason to take agentic commerce seriously now.

Just as mobile optimisation and HTTPS once went from competitive advantage to expected standard, the infrastructure for agentic commerce is quickly heading the same way. The question is no longer whether, but when and how.

Our guide to agentic commerce explains how to prepare your online shop in practice – and what is actually live, and where.