ACP: The Execution Layer Letting AI Agents Buy Without Leaving Chat

If UCP lets agents discover what you sell, the Agentic Commerce Protocol — ACP — lets them actually buy it. ACP is the execution layer of agentic commerce: the standard that lets an AI agent complete a purchase autonomously, on a user's behalf, without redirecting them to a checkout page.

The Execution Layer

ACP governs the moment of transaction. Once an agent has discovered a merchant via UCP and the user has authorized a purchase, ACP defines how the payment is executed — securely, with proper authentication, and without the friction of leaving the conversation.

The protocol is governed jointly by OpenAI and Stripe, which is not accidental. OpenAI owns the conversational surface where agentic purchases originate; Stripe owns the payment infrastructure that settles them. ACP is the connective tissue between the two.

How ACP Works

The core primitive is the Stripe Payment Token (SPT) — a tokenized, scoped authorization that lets an agent initiate a payment without ever holding raw card data. The user authorizes a spending envelope; the agent presents the SPT at checkout; Stripe settles the transaction within the authorized limits.

ChatGPT Instant Checkout is ACP in production. When a user asks ChatGPT to buy something and the purchase completes without leaving the chat, that flow is ACP executing end to end — discovery, authorization, tokenized payment, and confirmation, all within the conversational interface.

Delegated payment flows are the broader pattern. A user delegates a purchasing task to an agent with constraints — a budget, a category, a deadline — and ACP provides the standardized mechanism for the agent to execute within those constraints across any ACP-compatible merchant.

Why ACP Matters

ACP collapses the distance between intent and purchase. In the classic e-commerce funnel, a user searches, clicks, lands, browses, adds to cart, and checks out — six steps, each a drop-off point. ACP lets a single natural-language instruction ("order my usual groceries," "book the cheapest flight to JFK tonight") resolve to a completed transaction.

For merchants, ACP-compatible checkout becomes a requirement to participate in agentic demand. For platforms, owning the execution layer — as OpenAI and Stripe do — is a structural advantage in the agentic commerce stack.