Gate an existing API (proxy)

The idea

Already have an API, in Python, Go, Rails, anything? You don’t have to rewrite it to charge for it. proxyTo(origin) is a ready-made handler that forwards a paid request to your existing backend, untouched, and rejects unpaid ones before they ever reach it. Deploy it on the edge in front of your API; the API never changes and never sees an unpaid request.

import { createPaywall, toWorker, proxyTo } from '@piprail/sdk'

const gate = createPaywall({ chain: 'base', amount: '0.01', payTo: '0xYourWallet' })

// A Cloudflare Worker that charges 0.01 USDC per request to https://api.example.com:
export default toWorker(gate, proxyTo('https://api.example.com'))

proxyTo preserves the method, path, query, body, and headers; it strips the x402 proof headers so they don’t leak upstream. The origin only ever receives requests that have already paid. An unpaid request gets a 402 and never reaches your backend.

Scaffold it

The fastest way is the scaffolder’s proxy mode, which generates a complete, mainnet-default edge proxy:

npm create @piprail -- my-gateway \
  --sell proxy \
  --origin https://api.example.com \
  --host cloudflare \
  --pay-to 0xYourPublicAddress \
  --amount 0.01

The generated worker forwards paid traffic to your origin and serves /.well-known/x402 so AI agents can discover and price it. → Scaffold a merchant

How it compares

Cloudflare ships an x402-proxy template too, but it defaults to testnet and routes settlement through a facilitator. PipRail’s proxy is mainnet-default and facilitator-free: it verifies each payment locally against your own RPC, and receiving needs only your public address: no key, no account, no middleman.

Notes

• The proxy is edge-only (Cloudflare Workers / Vercel Edge Functions), because that’s where a low-latency forward belongs. For a Node/Express app you own, gate the route directly with requirePayment instead.
• It gates every path. Carve out free routes by checking new URL(request.url).pathname before the gate, exactly like the scaffolded /.well-known/x402 route does.
• proxyTo composes with both framework adapters: toWorker(gate, proxyTo(origin)) for the { fetch } export, or toFetchHandler(gate, proxyTo(origin)) for a bare handler.