ACP Core Concepts

1.1 ACP’s Role in AI Agentic Commerce

ACP (Agentic Commerce Protocol) was created by Stripe as an open standard defining the protocol for programmatic commerce interactions. OpenAI ChatGPT is the first implementer, but ACP is designed to be adoptable by any AI platform. Key distinction: UCP is a universal cross-platform protocol (co-initiated by Google, Shopify, and others), while ACP was created by Stripe and first implemented within the ChatGPT ecosystem.

1.2 The Four-Party Model

ACP defines four participants:

Buyer
  | interacts via AI conversation
Agent (e.g., ChatGPT)
  | calls Checkout API
Business (Merchant)
  | delegates payment processing
Payment Provider (e.g., Stripe)

Participant	Role	Example
Buyer	Consumer who initiates a purchase intent	ChatGPT user
Agent	AI that executes commerce operations on behalf of the buyer	ChatGPT
Business	Merchant providing products and checkout services	Online retailer
Payment Provider	Securely processes payment credentials	Stripe

1.3 Two Independent Systems

ACP is not a single API. It consists of two entirely independent systems:

System 1: Product Feed (Product Data Sync)

Direction: Merchant to OpenAI platform Merchants push product catalog data to OpenAI. ChatGPT uses this data to surface relevant products in user conversations.

Merchant Product Database
  | SFTP file upload (daily full snapshots)
  | REST API (real-time incremental updates)
OpenAI Product Feed System
  | indexing and understanding
ChatGPT surfaces products in conversations

Supported data submission methods:

SFTP push: Parquet (zstd compression) / jsonl.gz / csv.gz / tsv.gz
REST API: Feeds + Products + Promotions endpoints

System 2: Agentic Checkout (Transaction Processing)

Direction: AI agent to Merchant server When a user confirms a purchase, the AI agent calls Checkout API endpoints hosted by the merchant to complete the transaction.

User: "I want to buy these shoes"
  |
ChatGPT -> POST /checkout_sessions (create checkout session)
ChatGPT -> POST /checkout_sessions/:id (update shipping address)
  |
Stripe Delegate Payment API -> obtain vault token (vt_...)
  |
ChatGPT -> POST /checkout_sessions/:id/complete (submit payment)
  |
Merchant confirms order

1.4 Checkout Session State Machine

Each checkout session has a status that transitions through the following flow:

incomplete
  |
not_ready_for_payment
  | (shipping address, buyer info completed)
ready_for_payment
  | (payment submitted)
complete_in_progress
  |
completed

Complete status enumeration:

Status	Description
`incomplete`	Session just created, information is incomplete
`not_ready_for_payment`	Missing required information (address, shipping method, etc.)
`requires_escalation`	Requires human intervention
`authentication_required`	Requires 3DS or other identity verification
`ready_for_payment`	All information present, ready to pay
`pending_approval`	Awaiting approval
`complete_in_progress`	Payment is being processed
`completed`	Transaction complete
`in_progress`	Processing
`canceled`	Canceled
`expired`	Expired

1.5 Delegate Payment

ACP solves payment security through the Delegate Payment API. The AI agent never passes raw card numbers to the merchant. Flow:

The AI agent sends payment credentials to Stripe’s POST /agentic_commerce/delegate_payment
Stripe tokenizes the card and returns a vault token (format vt_...)
The AI agent passes the vault token (not the card number) to the merchant’s /checkout_sessions/:id/complete
The merchant uses the vault token to request the actual charge from Stripe

Security guarantee: The merchant never touches raw card numbers. PCI compliance is handled by Stripe.

1.6 Price Format

All monetary amounts in ACP use ISO 4217 minor currency units:

Actual Amount	ACP Value	Currency
$79.99	7999	USD
$49.50	4950	USD
EUR 29.00	2900	EUR
JPY 1000 (no decimals)	1000	JPY

{
  "amount": 7999,
  "currency": "USD"
}

Amounts must be greater than or equal to 0. Currency uses ISO 4217 three-letter codes.

1.7 Capabilities Negotiation

ACP supports capability negotiation between merchants and AI agents. Merchants declare their supported capabilities in the Checkout Session creation response:

Payment handlers: Supported payment methods (handler ID, version, spec URL, schema)
Interventions: Whether redirects, human intervention, and other interaction modes are supported
Extensions: Extension capability declarations (semantic versioning + optional date, JSONPath defines extension fields)

1.8 ACP vs. Traditional E-Commerce vs. UCP

Dimension	Traditional E-Commerce	UCP	ACP
Product Display	Merchant’s own website	AI agent calls merchant API	ChatGPT surfaces from Feed data
Data Control	Entirely on merchant side	Merchant side (API endpoints)	Pushed to OpenAI + merchant-hosted Checkout
Payment	Direct payment gateway	Payment Token Exchange	Delegate Payment (vault token)
Orders	Merchant system managed	Standardized Order API	Order returned after Checkout completion

Next chapter: Product Data Format — Complete field specifications for Product objects, Variants, pricing, media, and availability

ACP Agentic Commerce Protocol ACP product data object field specification

Start

Learning Paths

Getting Started with AI Commerce

OTR Open Trust Registry

UCP Universal Commerce Protocol

ACP Agentic Commerce Protocol

MCP Model Context Protocol

SEO for the AI Era

ORBEXA Integrated Solution

Templates & Prompts

Glossary

ACP protocol architecture and core concepts

ACP Core Concepts

1.1 ACP’s Role in AI Agentic Commerce

1.2 The Four-Party Model

1.3 Two Independent Systems

System 1: Product Feed (Product Data Sync)

System 2: Agentic Checkout (Transaction Processing)

1.4 Checkout Session State Machine

1.5 Delegate Payment

1.6 Price Format

1.7 Capabilities Negotiation

1.8 ACP vs. Traditional E-Commerce vs. UCP

​ACP Core Concepts

​1.1 ACP’s Role in AI Agentic Commerce

​1.2 The Four-Party Model

​1.3 Two Independent Systems

​System 1: Product Feed (Product Data Sync)

​System 2: Agentic Checkout (Transaction Processing)

​1.4 Checkout Session State Machine

​1.5 Delegate Payment

​1.6 Price Format

​1.7 Capabilities Negotiation

​1.8 ACP vs. Traditional E-Commerce vs. UCP

ACP Core Concepts

1.1 ACP’s Role in AI Agentic Commerce

1.2 The Four-Party Model

1.3 Two Independent Systems

System 1: Product Feed (Product Data Sync)

System 2: Agentic Checkout (Transaction Processing)

1.4 Checkout Session State Machine

1.5 Delegate Payment

1.6 Price Format

1.7 Capabilities Negotiation

1.8 ACP vs. Traditional E-Commerce vs. UCP