PayGate 402

Turn any API or MCP server into a paid service

table of contents

• install
• usage
• api
• configuration
• payment providers
• http 402
• contributing
• license

install

npm install paygate-402

usage

wrap an existing API

import { PayGate } from 'paygate-402';

const paygate = new PayGate({
  provider: 'stripe',
  apiKey: process.env.STRIPE_KEY,
  pricing: {
    perRequest: 0.01,
    perToken: 0.0001
  }
});

// wrap your express app
app.use(paygate.middleware());

// or wrap specific routes
app.get('/api/premium', paygate.protect(), (req, res) => {
  res.json({ data: 'premium content' });
});

wrap an MCP server

import { MCPPayGate } from 'paygate-402/mcp';
import { Server } from '@modelcontextprotocol/sdk/server/index.js';

const server = new Server({
  name: 'my-mcp-server',
  version: '1.0.0'
});

const paygate = new MCPPayGate({
  provider: 'stripe',
  apiKey: process.env.STRIPE_KEY,
  pricing: {
    perTool: {
      'expensive_tool': 0.10,
      'cheap_tool': 0.01
    }
  }
});

paygate.wrap(server);

client usage

import axios from 'axios';

const response = await axios.get('https://api.example.com/premium', {
  headers: {
    'Authorization': 'Bearer YOUR_PAYMENT_TOKEN'
  }
});

// handle 402 Payment Required
if (response.status === 402) {
  const paymentUrl = response.headers['payment-url'];
  console.log('Payment required:', paymentUrl);
}

api

PayGate(options)

Creates a new payment gateway instance.

Options:

Option	Type	Description
provider	string	Payment provider ('stripe', 'paypal', 'lightning')
apiKey	string	Provider API key
pricing	PricingConfig	Pricing configuration
allowCredits	boolean	Allow prepaid credits (default: true)
quotaLimits	QuotaConfig	Optional rate limits per user

paygate.middleware()

Returns Express middleware that intercepts requests and enforces payment.

paygate.protect(options?)

Returns middleware for protecting specific routes.

Options:

Option	Type	Description
price	number	Override default price for this route
creditsRequired	number	Require specific credit amount

paygate.createPaymentToken(userId, credits)

Generates a payment token for a user with prepaid credits.

Returns: Promise<string>

paygate.checkBalance(token)

Checks remaining balance for a payment token.

Returns: Promise<{ credits: number, spent: number }>

configuration

pricing models

// per-request pricing
{
  pricing: {
    perRequest: 0.05
  }
}

// token-based pricing (for LLM APIs)
{
  pricing: {
    perToken: 0.0001,
    perInputToken: 0.00005,
    perOutputToken: 0.00015
  }
}

// route-specific pricing
{
  pricing: {
    routes: {
      '/api/basic': 0.01,
      '/api/premium': 0.10,
      '/api/enterprise': 1.00
    }
  }
}

// credit bundles
{
  pricing: {
    bundles: [
      { credits: 100, price: 9.99 },
      { credits: 500, price: 44.99 },
      { credits: 1000, price: 79.99 }
    ]
  }
}

payment providers

stripe

{
  provider: 'stripe',
  apiKey: process.env.STRIPE_SECRET_KEY,
  webhookSecret: process.env.STRIPE_WEBHOOK_SECRET
}

paypal

{
  provider: 'paypal',
  clientId: process.env.PAYPAL_CLIENT_ID,
  clientSecret: process.env.PAYPAL_CLIENT_SECRET,
  sandbox: true
}

lightning network

{
  provider: 'lightning',
  lndHost: process.env.LND_HOST,
  macaroon: process.env.LND_MACAROON,
  cert: process.env.LND_CERT
}

http 402

This project uses HTTP status code 402 (Payment Required) as defined in RFC 7231. When a request requires payment, the server responds with:

HTTP/1.1 402 Payment Required
Payment-URL: https://pay.example.com/checkout/xyz123
Payment-Amount: 0.05
Payment-Currency: USD
Content-Type: application/json

{
  "error": "payment_required",
  "amount": 0.05,
  "currency": "USD",
  "payment_url": "https://pay.example.com/checkout/xyz123"
}

contributing

PRs welcome. Open an issue first for big changes.

Run tests:

npm test

license

MIT