Architecture
The Agentic Commerce Protocol (ACP) defines how four parties interact to complete a purchase: buyers, agents, sellers, and payment providers. This page explains how these components connect and where trust boundaries exist.
Components
Buyer
The human who wants to purchase something. Buyers interact with agents through natural conversation, expressing intent like "I want to buy wireless headphones." They review checkout details, select options, and authorize payment—all within the agent interface.
Agent
An AI platform that orchestrates the checkout experience. Agents are responsible for:
- Interpreting buyer intent and translating it into structured API calls
- Rendering checkout UI to display products, options, and totals
- Managing the checkout flow by creating, updating, and completing sessions
- Collecting payment credentials and obtaining delegated payment tokens
- Communicating status back to the buyer in real time
Seller
The merchant who sells products. Sellers implement the Checkout API and remain the merchant of record. They are responsible for:
- Calculating prices including discounts, taxes, and shipping
- Managing inventory and product availability
- Processing payments through their payment provider
- Fulfilling orders after successful payment
Payment Provider
A payment service provider (PSP) that handles payment tokenization and processing. Payment providers:
- Tokenize payment credentials with allowance constraints via Delegate Payment
- Process charges when sellers complete checkouts
- Enforce spending limits defined in the allowance
Specifications
ACP consists of two complementary specifications:
| Specification | Purpose | Parties |
|---|---|---|
| Agentic Checkout | Manages the checkout session lifecycle | Agent ↔ Seller |
| Delegate Payment | Tokenizes payment credentials with constraints | Agent ↔ PSP |
Agentic Checkout
Defines the REST API that agents use to conduct checkouts with sellers. The specification covers:
- Creating checkout sessions with items and buyer information
- Retrieving and updating session state
- Selecting fulfillment options
- Completing checkout with payment
- Canceling sessions
Delegate Payment
Defines how agents obtain payment tokens with controlled usage. The specification covers:
- Tokenizing card credentials
- Setting allowance constraints (amount, currency, expiration, merchant)
- Including risk signals for fraud prevention
- Receiving vault tokens for use in checkout completion
Data flow
A typical purchase flows through these stages: