merx-x402

Express middleware for x402 payments on TRON and Base via MERX facilitator.

Install

npm install merx-x402

Usage

import express from 'express'
import { requirePayment } from 'merx-x402'

const app = express()

// TRON USDT payment ($0.10 per call)
app.get('/api/data', requirePayment({
  amount: '0.10',
  recipient: 'TYourTronAddress',
}), (req, res) => {
  console.log('Paid by:', req.payment.payer, 'tx:', req.payment.txid)
  res.json({ data: 'premium content' })
})

// Base USDC payment
app.get('/api/evm', requirePayment({
  amount: '0.01',
  recipient: '0xYourAddress',
  network: 'eip155:8453',
  asset: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913',
}), (req, res) => {
  res.json({ data: 'paid via Base' })
})

app.listen(3000)

How it works

1. Client calls your API without payment
2. Middleware returns 402 with PAYMENT-REQUIRED header (x402 v2 format)
3. Client pays (USDT on TRON or USDC on Base) and retries with PAYMENT-SIGNATURE header
4. Middleware verifies + settles via MERX facilitator
5. Your handler runs with req.payment containing txid, payer, amount

Config

| Option | Required | Default | Description | |--------|----------|---------|-------------| | amount | yes | - | Price in USD (e.g. '0.10') | | recipient | yes | - | Your TRON (T...) or EVM (0x...) address | | scheme | no | 'exact' | 'exact' or 'upto' | | network | no | 'tron:0x2b6653dc' | CAIP-2 network identifier | | asset | no | USDT contract | Token contract address | | facilitator | no | https://x402.merx.exchange | Facilitator URL | | apiKey | no | - | MERX API key (unlimited rate) | | description | no | 'Payment required' | Human-readable description |

Facilitator

MERX is the first x402 facilitator for TRON. Free, no API key required (100 req/day). Get unlimited access at merx.exchange/dashboard/api-keys.

Supported networks: tron:0x2b6653dc (USDT, USDC, USDD), eip155:8453 (USDC on Base).

License

MIT