ACP Merchant Demo

Reference implementation of the Agentic Commerce Protocol (ACP) — the open standard co-developed by Stripe and OpenAI enabling AI agents to complete purchases on behalf of users.

Live demo: acp-merchant-demo.vercel.app/demo

Highlights

• Full ACP Protocol — CreateCheckout, UpdateCheckout, CompleteCheckout endpoints per spec
• Real Stripe Integration — PaymentIntents created on every completed checkout
• Interactive Demo — Visual representation of Agent ↔ Merchant protocol flow
• Webhook Support — Handles payment_intent.succeeded, payment_intent.payment_failed
• Production Ready — Zod validation, error handling, structured logging

_{Checkout Flow — Real-time ACP protocol visualization with live API responses.}

Product Selection — Click to initiate ACP checkout.	Order Complete — Real PaymentIntent in Stripe.
Request Log — Full protocol request/response history.	Stripe Transaction — Real payment with acp_checkout_id metadata linking systems.

Why This Matters

ACP represents a fundamental shift in e-commerce: instead of users navigating checkout pages, AI agents handle the entire purchase flow programmatically. This demo implements the merchant side of that protocol.

What ACP Solves	How
N×M integration problem	Universal protocol — each agent/merchant implements once
Trust & payment security	SharedPaymentToken with scoped permissions
UI control	Agent renders UI, merchant controls pricing/fulfillment

Demo (60 seconds)

1. Visit acp-merchant-demo.vercel.app/demo
2. Click any product → Checkout card appears, JSON updates (real POST /api/acp/checkout)
3. Change shipping → Totals recalculate (real POST /api/acp/checkout/update)
4. Click "Pay" → Purchase completes (real POST /api/acp/checkout/complete)
5. Expand "ACP REQUESTS" → View full request/response history
6. Check Stripe Dashboard → PaymentIntent created

Architecture

flowchart LR
  subgraph Agent["AI Agent (ChatGPT/Claude)"]
    UI["Chat Interface"]
  end

  subgraph Merchant["ACP Merchant Demo (This Project)"]
    direction TB
    API["API Routes<br/>/api/acp/*"]
    CS["Checkout Service"]
    PS["Payment Service"]
    STORE["In-Memory Store"]
  end

  subgraph External["External Services"]
    STRIPE["Stripe API"]
  end

  UI -->|"POST /checkout"| API
  UI -->|"POST /checkout/update"| API
  UI -->|"POST /checkout/complete"| API
  
  API --> CS
  CS --> STORE
  CS --> PS
  PS --> STRIPE
  
  STRIPE -->|"PaymentIntent"| PS
  PS -->|"Order confirmed"| API
  API -->|"JSON response"| UI

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Tech Stack:

• Next.js 14 (App Router, TypeScript)
• Stripe SDK
• Zod validation
• Tailwind CSS
• Vercel (deployment)

API Endpoints

Endpoint	Method	Description
/api/acp/checkout	POST	Create checkout session
/api/acp/checkout/update	POST	Update shipping, address, email
/api/acp/checkout/complete	POST	Complete with payment token
/api/acp/webhooks	POST	Handle Stripe webhook events
/api/health	GET	Health check with store stats
/.well-known/acp.json	GET	ACP discovery endpoint

ACP Protocol Flow

sequenceDiagram
    participant User
    participant Agent as AI Agent
    participant Merchant as ACP Merchant
    participant Stripe

    User->>Agent: "Buy running shoes"
    Agent->>Merchant: POST /checkout {items}
    Merchant-->>Agent: {checkout_id, shipping_options, total}
    
    Agent->>User: "Shipping: Standard or Express?"
    User->>Agent: "Standard"
    
    Agent->>Merchant: POST /checkout/update {shipping_option}
    Merchant-->>Agent: {updated_total, ready_for_payment}
    
    Agent->>User: "Total: $135.98. Confirm?"
    User->>Agent: "Yes"
    
    Agent->>Stripe: Request SharedPaymentToken
    Stripe-->>Agent: {payment_token}
    
    Agent->>Merchant: POST /checkout/complete {payment_token}
    Merchant->>Stripe: Create PaymentIntent
    Stripe-->>Merchant: {payment_intent_id}
    Merchant-->>Agent: {order_id, status: completed}
    
    Agent->>User: "Order confirmed! 🎉"

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Quickstart

# Clone
git clone https://github.com/nickcarndt/acp-merchant-demo.git
cd acp-merchant-demo

# Install
npm install

# Configure
cp .env.example .env.local
# Edit .env.local with your Stripe keys

# Run
npm run dev

Open http://localhost:3000/demo

Environment Variables

Variable	Description	Required
STRIPE_SECRET_KEY	Stripe API secret key (test mode)	Yes
STRIPE_WEBHOOK_SECRET	Webhook signing secret	For webhooks
ACP_AUTH_TOKEN	Bearer token for ACP endpoints	Yes
NEXT_PUBLIC_ACP_AUTH_TOKEN	Client-side auth token	For demo UI

Deploy (Vercel)

# Deploy
vercel

# Set environment variables in Vercel dashboard
# Redeploy
vercel --prod

Webhook Setup:

1. Stripe Dashboard → Developers → Webhooks
2. Add endpoint: https://your-app.vercel.app/api/acp/webhooks
3. Select events: payment_intent.succeeded, payment_intent.payment_failed
4. Copy signing secret to Vercel env vars

Testing

# Smoke test (local)
./test-acp.sh

# Smoke test (production)
./test-acp-prod.sh

Related Projects

Project	Description
MCP Server	AI agent tools for Stripe/Shopify (agent side)
Chatbot with Memory	Full-stack AI chatbot with MCP integration

Resources

• ACP Specification
• Stripe ACP Docs
• OpenAI Commerce Docs
• SharedPaymentToken

Author

Nicholas Arndt — GitHub · LinkedIn

License

MIT © 2025 Nicholas Arndt