acp-peptide-pharmacy

ACP Peptide Pharmacy

A full-stack demo storefront that combines the Agentic Commerce Protocol (ACP), Model Context Protocol (MCP), and optional Machine Payments Protocol (MPP) with Stripe test mode so Claude, Cursor, and other AI clients can browse products and place demo peptide orders.

Architecture

• backend/: Cloudflare Worker with ACP checkout, remote MCP (/mcp), optional MPP gate
• frontend/: static storefront (GitHub Pages) + mpp-demo.html overview
• mcp-config/: MCP client configuration examples
• IMPLEMENTATION_NOTES.md: frozen MPP route policy for this repo

Live references:

• Storefront: tech-sumit.github.io/acp-peptide-pharmacy
• Worker API: acp-peptide-pharmacy-backend.tech-sumit.workers.dev

Machine Payments Protocol (MPP) on POST /mcp

This Worker integrates MPP using Stripe shared payment tokens (SPTs) via the official mppx server middleware, following Stripe’s MPP guide.

Test mode only (including production Worker)

• The deployed Worker follows the same rules as local dev: only Stripe test keys (sk_test_...). Live keys (sk_live_...) are rejected — there are no real card charges on the public demo; MPP is a concept demo using Stripe test mode.
• All MPP charges in this demo are sandbox amounts (currently $0.01 USD per paid tools/call request).
• ACP checkout remains a simulated merchant flow (demo tokens), separate from MPP access fees.
• GET / and GET /health include mpp_demo_billing (and unpaid tools/call responses include x-mpp-stripe-mode: test) so clients can see that billing is test-only.

When MPP is active

If both STRIPE_SECRET_KEY and MPP_SECRET_KEY are configured as Cloudflare secrets:

1. Handshake and discovery (initialize, tools/list, ping, notifications, etc.) stay free so Streamable HTTP clients (Cursor, mcp-remote) can connect without MPP.
2. Paid JSON-RPC (notably tools/call) without a valid Authorization: Payment ... credential returns 402 with a WWW-Authenticate: Payment challenge (RFC 9457 problem body).
3. After the client pays (Stripe test mode + SPT) and retries with the credential, the Worker runs the tool and may attach a Payment-Receipt header on success.

If those secrets are omitted, POST /mcp behaves as before (no payment gate) so CI and local dev stay simple.

Configure secrets

cd backend

# Stripe test secret from https://dashboard.stripe.com/test/apikeys
npx wrangler secret put STRIPE_SECRET_KEY

# 32-byte key, base64 — binds challenges (mpp.dev / mppx)
openssl rand -base64 32 | npx wrangler secret put MPP_SECRET_KEY

Manual smoke test (curl)

Handshake (expect 200 when MPP is configured):

curl -i -X POST "https://YOUR-WORKER.workers.dev/mcp" \
  -H "content-type: application/json" \
  -H "accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"curl","version":"0"}}}'

Unpaid tools/call (expect 402 when MPP is configured):

curl -i -X POST "https://YOUR-WORKER.workers.dev/mcp" \
  -H "content-type: application/json" \
  -H "accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"list_products","arguments":{}}}'

Paid retry for tool calls requires an MPP-aware client (for example npx mppx against a local dev server, or a small app using Stripe Elements to mint an SPT per Stripe’s docs). See mcp-config/README.md.

Local development

cd backend
npm install
npm run test
npm run dev

Learn more

• Blog walkthrough: sumitagrawal.dev/blog/machine-payments-protocol-mcp-acp/ (after the portfolio PR is merged)