---
name: mpp-proxy
description: >
  Implement MPP payment proxies — wrap existing APIs with HTTP 402 payment
  gates without modifying the upstream service. Use when monetizing third-party
  APIs, adding payment layers to existing services, or building API
  marketplaces.
---

# MPP Payment Proxy

## Before writing code

**Fetch live docs**:
1. Fetch `https://www.npmjs.com/package/mppx` for the proxy handler API and configuration
2. Web-search `mppx proxy payment 402 existing API monetize` for proxy implementation patterns
3. Web-search `site:github.com stripe-samples machine-payments proxy` for official proxy sample code
4. Fetch `https://developers.cloudflare.com/agents/agentic-payments/mpp/` for Cloudflare Workers proxy patterns

## Conceptual Architecture

### What the Proxy Does

The MPP proxy wraps an existing upstream API with a payment gate, requiring clients to pay before their requests are forwarded. The upstream API is unmodified — it never sees the payment flow.

```
Client → MPP Proxy (402 challenge-response) → Upstream API
         ↑ payment gate                       ↑ unmodified
```

### Use Cases

- **API monetization** — Charge for access to your own internal APIs
- **Third-party reselling** — Add payment layer on top of third-party APIs (with permission)
- **API marketplace** — Proxy multiple upstream APIs through a single payment gateway
- **Rate-limiting replacement** — Replace API key + rate limits with pay-per-use
- **Value-added wrapper** — Add caching, transformation, or enrichment on top of upstream APIs

### Proxy Architecture

```
┌──────────────┐     ┌──────────────────────┐     ┌──────────────┐
│  AI Agent    │────→│    MPP Proxy          │────→│  Upstream    │
│  (Client)    │←────│  1. 402 Challenge     │←────│  API         │
│              │     │  2. Verify Payment    │     │  (Unmodified)│
│              │     │  3. Forward Request   │     │              │
│              │     │  4. Return + Receipt  │     │              │
└──────────────┘     └──────────────────────┘     └──────────────┘
```

### mppx Proxy Handler

The `mppx` SDK provides a dedicated proxy handler:

```typescript
import { Mppx, tempo } from 'mppx/server';

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

// Proxy all requests to upstream with payment gate
app.all('/api/*', mppx.charge({ amount: '100' }), async (c) => {
  const upstreamUrl = `https://upstream-api.com${c.req.path}`;
  const response = await fetch(upstreamUrl, {
    method: c.req.method,
    headers: c.req.headers,
    body: c.req.method !== 'GET' ? await c.req.text() : undefined,
  });
  return new Response(response.body, {
    status: response.status,
    headers: response.headers,
  });
});
```

### Cloudflare Workers Proxy

For edge-deployed proxies:

```typescript
// Cloudflare Workers + MPP proxy pattern
export default {
  async fetch(request, env) {
    // MPP middleware handles 402 challenge-response
    // On successful payment, forwards to upstream
  }
};
```

### Pricing Strategies

| Strategy | Description |
|----------|-------------|
| **Flat rate** | Same price for all requests |
| **Endpoint-based** | Different prices per API route |
| **Payload-based** | Price varies by request/response size |
| **Metered** | Session-based, charged per unit consumed |
| **Tiered** | Volume discounts (first 100 at $X, next 1000 at $Y) |

### Request/Response Handling

- **Headers** — Forward client headers to upstream (strip `Authorization: Payment`)
- **Body** — Forward request body unchanged
- **Response** — Add `Payment-Receipt` header to upstream response
- **Errors** — Distinguish between payment errors (402) and upstream errors (pass through)

### Multi-Upstream Proxy

Route to different upstreams based on the path:

```typescript
const upstreams = {
  '/ai/': 'https://api.openai.com',
  '/data/': 'https://api.data-vendor.com',
  '/search/': 'https://api.search-engine.com',
};
```

### Best Practices

- Strip payment headers before forwarding to upstream
- Add service discovery (`/openapi.json`) describing proxied endpoints
- Implement caching for idempotent GET requests to reduce upstream calls
- Add response transformation if needed (but keep it minimal)
- Monitor upstream availability and return appropriate errors
- Set up health checks that verify both proxy and upstream availability
- Consider latency — the proxy adds the payment negotiation round-trip

Fetch the latest mppx proxy documentation and Cloudflare MPP integration guide for exact proxy API, configuration options, and edge deployment patterns before implementing.


---
Source attribution: OrcaQubits
Original project: https://github.com/OrcaQubits/agentic-commerce-skills-plugins/blob/30cd25c74c8aa7dc49b3ec4847d463f6104439f6/dist/codex/stripe-mpp/skills/mpp-proxy/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Dave AI.

## Upstream license notice

MIT License

Copyright (c) 2024-2026 OrcaQubits AI (https://orcaqubits-ai.com)

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Dave AI resource metadata

Creator / publisher: OrcaQubits
Original project: https://github.com/OrcaQubits/agentic-commerce-skills-plugins/blob/30cd25c74c8aa7dc49b3ec4847d463f6104439f6/dist/codex/stripe-mpp/skills/mpp-proxy/SKILL.md
Attribution basis: Source repository record

Fields of work: Marketing, Sales
Roles: Business Development, Growth Marketer, Marketing Analyst, Product Marketer, Sales Engineer
Specialties: API
Tools: Cloudflare Workers, Mppx
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: 25167c8d95aea85845fc7237673652fb43bfd1d6a18a0cd050ee71de0db7548c