ACP — Agentic Commerce Protocol

Maintainers: OpenAI, Stripe, Meta (Founding Maintainers / TSC) · Repo: agentic-commerce-protocol/agentic-commerce-protocol · Stable revision: spec/2026-04-17/

ACP is the open spec behind OpenAI’s Buy It in ChatGPT surface. It defines how a buyer’s AI agent transacts with a merchant — cart, checkout, fulfillment, delegated payment — and integrates natively with Stripe (and any other PSP that ships an ACP handler).

For a side-by-side technical breakdown against UCP and AP2, see the comparison page.

Capabilities

Cart — create, update, line-item adjustments
Checkout — initiate, confirm, capture
Discounts & promotions — rich price_adjustment model (richest of the three protocols)
Fulfillment — shipping options, address validation
Delegated payments — agent acts on behalf of buyer via platform bearer token

What’s not in ACP today: catalog/product feed, refunds, disputes, normative request signing. See Issue #4 for the explicit out-of-scope decision on request integrity.

Integration sketch

A minimal delegate_payment + checkout flow. Endpoints below use the example pattern from the spec; replace with your merchant’s actual ACP endpoint.


// 1. Agent obtains a delegated payment authorization for the buyer.
const delegation = await fetch('https://merchant.example.com/acp/delegate_payment', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${PLATFORM_TOKEN}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    buyer_id: 'buyer_123',
    max_amount: { value: '49.99', currency: 'USD' },
    valid_until: '2026-05-17T00:00:00Z',
  }),
}).then(r => r.json())
 
// 2. Create a cart.
const cart = await fetch('https://merchant.example.com/acp/carts', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${PLATFORM_TOKEN}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    items: [{ sku: 'WIDGET-001', quantity: 1 }],
  }),
}).then(r => r.json())
 
// 3. Complete checkout using the delegation.
const order = await fetch(`https://merchant.example.com/acp/carts/${cart.id}/checkout`, {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${PLATFORM_TOKEN}`,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    payment: { delegation_id: delegation.id },
    shipping_address: { /* ... */ },
  }),
}).then(r => r.json())

The Bearer token is platform-issued (typically by OpenAI for ChatGPT-originated traffic, or by the merchant directly). There is no spec-level request signing — verifying that a given call really came from the named agent is currently a platform concern.

Reference implementations

vercel/acp-handler — Next.js/Vercel handler
locus-technologies/acp-demo — reference implementation
NVIDIA-AI-Blueprints/Retail-Agentic-Commerce — NVIDIA blueprint covering both ACP and UCP

xpay✦ contributions to ACP

PR #251 — README’s Repo Structure section was missing changelog/2026-01-16.md (the file exists on disk alongside the other dated changelogs). Small minor-improvement fix.

Longer-term: scoping a SEP to adopt RFC 9421 (HTTP Message Signatures) at the spec level, citing UCP’s reference verifier as precedent. The aim is a single normative request-integrity story instead of N per-platform bearer schemes — see Issue #4 for the existing out-of-scope discussion.

Also tracking Issue #97 (Idempotency-Key TTL guidance) — a Stripe TSC member has signalled willingness to sponsor.