ACP Explained: OpenAI & Stripe's Agentic Commerce Protocol

What is ACP?

The Agentic Commerce Protocol (ACP) is an open standard developed by OpenAI and Stripe that enables AI agents to complete purchases on behalf of users.

You've probably seen the demos: someone asks ChatGPT to find a product, ChatGPT shows options, user clicks "Buy," and the purchase completes—all without leaving the chat.

That's ACP in action. It's the plumbing that makes "Instant Checkout" work.

UCP vs ACP: What's the Difference?

Quick comparison:

Bottom line: You probably want both. UCP for Google's ecosystem, ACP for ChatGPT. Different protocols for different platforms.

How ACP Works (Technical)

ACP defines a RESTful HTTP interface with four core endpoints:

1. Create Checkout

When a user starts buying, the AI agent hits your Create endpoint with a product SKU. You return cart data, pricing, available options.

2. Update Checkout

User changes quantity, selects shipping method, enters details. Each change hits this endpoint and you return updated checkout state.

3. Complete Checkout

When the user confirms, you receive a Shared Payment Token. This is the magic—Stripe handles payment credentials securely.

4. Cancel Checkout

If the user abandons, this endpoint releases any held inventory.

The Shared Payment Token

This is ACP's clever innovation. Here's the problem it solves:

AI agents shouldn't handle credit card numbers. That's a security nightmare. But merchants need to charge customers somehow.

Stripe's solution: the Shared Payment Token (SPT).

1. User saves payment method with Stripe (one time)
2. When they buy via ChatGPT, Stripe issues a temporary token
3. Token is scoped to specific merchant + cart total
4. ChatGPT passes token to merchant via API
5. Merchant charges token through Stripe (or another processor)

The AI never sees actual payment details. Security maintained.

Platform Support

ACP is rolling out through the "Agentic Commerce Suite" to multiple platforms:

• ✓Etsy - Live now for US sellers
• →Shopify - 1M+ merchants "coming soon"
• →WooCommerce - Rolling out
• →BigCommerce - Rolling out
• →Squarespace - Rolling out
• →Wix - Rolling out

If your platform is listed, keep an eye out for native integration options. Much easier than building from scratch.

What You Need to Implement ACP

If you want to build ACP support yourself, you'll need:

• 1. REST API Endpoints
  Four endpoints following the Agentic Checkout Spec
• 2. Stripe Integration
  Or another Delegated Payment Spec-compatible PSP
• 3. Webhooks
  To notify ChatGPT of order events (with HMAC signing)
• 4. OpenAI Certification
  Pass conformance checks to go live

If you already process payments with Stripe, they claim you can enable agentic payments in as little as one line of code. Reality may vary.

Should You Wait or Act Now?

Here's our honest take: