MPP Stripe Payment Method (Cards via SPTs)

Before writing code

Fetch live docs:

1. Fetch https://docs.stripe.com/agentic-commerce/concepts/shared-payment-tokens for the latest SPT API
2. Fetch https://docs.stripe.com/payments/machine/mpp for MPP + Stripe integration
3. Web-search site:docs.stripe.com shared_payment granted_token for SPT creation and usage API
4. Web-search mppx stripe payment method server configuration for mppx Stripe adapter setup

Conceptual Architecture

What Stripe Method Does in MPP

The Stripe payment method enables fiat/card payments within the MPP protocol. Instead of on-chain crypto transactions, the payment proof is a Shared Payment Token (SPT) — a one-time, merchant-scoped, amount-limited token that Stripe processes as a standard charge.

Flow: MPP + Stripe SPT

1. Agent → Server:        GET /resource
2. Server → Agent:        402 with Stripe payment challenge
3. Agent → Stripe:        Create SPT (or use pre-provisioned SPT)
4. Agent → Server:        GET /resource with SPT credential
5. Server → Stripe:       PaymentIntent.create with shared_payment_granted_token
6. Stripe → Server:       Payment confirmed
7. Server → Agent:        200 OK with Payment-Receipt

SPT Structure

{
  "id": "spt_...",
  "usage_limits": {
    "currency": "usd",
    "max_amount": 1000,
    "expires_at": 1711234567
  },
  "deactivated_at": null,
  "deactivated_reason": null
}

SPT Creation (Agent-Side)

POST https://api.stripe.com/v1/test_helpers/shared_payment/granted_tokens

Parameters:
  payment_method: pm_card_visa
  usage_limits[currency]: usd
  usage_limits[max_amount]: 1000
  usage_limits[expires_at]: <unix_timestamp>
  seller_details[network_id]: <seller_network_id>
  seller_details[external_id]: <optional_external_id>

SPT Consumption (Server-Side)

POST https://api.stripe.com/v1/payment_intents

Parameters:
  amount: 500
  currency: usd
  shared_payment_granted_token: spt_...
  confirm: true

Server-Side mppx Configuration

import { Mppx, stripe } from 'mppx/server';

const mppx = Mppx.create({
  secretKey: process.env.MPP_SECRET_KEY,
  methods: [
    stripe.charge({
      // Stripe configuration for MPP
      // Automatically creates PaymentIntents when valid SPT credentials arrive
    }),
  ],
});

SPT Properties

• Single-use — Can only be charged once
• Time-bound — Agent-defined expiration window
• Amount-limited — Cannot exceed max_amount
• Currency-restricted — Only functions in specified currency
• Seller-scoped — network_id isolates tokens to specific merchants

SPT Webhook Events

Multi-Method Support

Combine Stripe with Tempo for maximum flexibility:

const mppx = Mppx.create({
  secretKey: process.env.MPP_SECRET_KEY,
  methods: [
    tempo.charge({ /* Tempo config */ }),
    stripe.charge({ /* Stripe config */ }),
  ],
});

Clients choose their preferred method when fulfilling the challenge.

Best Practices

• Set SPT max_amount to the exact payment amount (not higher)
• Set short expiration times — just enough for the payment to complete
• Implement SPT webhook listeners for lifecycle tracking
• Log SPT creation and usage for reconciliation (without sensitive data)
• Handle SPT expiration gracefully — re-provision if needed
• Never log full card numbers or CVCs (SPTs abstract away PCI data)

Fetch the latest Stripe SPT API documentation and mppx Stripe adapter docs for exact endpoint paths, request schemas, and configuration options before implementing.