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PipRail PipRail

Introduction

What is PipRail?

Section titled “What is PipRail?”

PipRail is three things, no server. It lets any HTTP request demand a crypto payment — the HTTP 402 Payment Required status, finally put to use — and lets any agent pay one automatically. There is no middleman: payments settle straight into your wallet, verified locally against your own RPC.

  • @piprail/sdk — a TypeScript SDK for x402 payments across any EVM chain, Solana, TON, Tron, NEAR, Sui, Aptos, Algorand, Stellar, and the XRP Ledger. npm install, name a chain, add a wallet, done.
  • @piprail/mcp — a Model Context Protocol server that wraps the SDK, handing any MCP client (Claude Desktop, Cursor, Claude Code, Windsurf, VS Code, Cline) a budget-bound wallet to pay x402 URLs autonomously, capped by a spend policy the model cannot exceed.
  • The marketing site — piprail.com, the pitch and the live demo.

There is no backend, no database, no auth, no dashboard, and no fee. It’s a tool you npm install, not a platform you sign up for.

The one idea

Section titled “The one idea”

Most payment SDKs ship an allowlist — a fixed set of chains they bless, and a facilitator in the middle that settles on your behalf. PipRail inverts both:

Chain details are data the caller passes, not an allowlist the SDK ships. Built-in presets (each with canonical USDC pre-filled) are a convenience; any other EVM chain works by passing a viem Chain or { id, rpcUrl }. No gatekeeping. And there’s no facilitator — your server verifies the payment itself, on-chain, against its own RPC.

One parameter picks everything:

const opts = { chain: 'base', token: 'USDC', amount: '0.10', payTo: '0xYourWallet' }
//             ^^^^^^^^^^^^^ — 'base' | 'bnb' | 'solana' | 'ton' | 'xrpl' | … picks the whole rail

x402 v2 §7 explicitly blesses this merchant-local shape (“resource servers MAY… host the endpoints themselves”), so being backendless is spec-supported, not a workaround.

The two sides

Section titled “The two sides”

PipRail has exactly two entry points — the seller and the buyer.

import { requirePayment, PipRailClient } from '@piprail/sdk'


// ACCEPT (server side) — turn a route paid-only.
// requirePayment(...) returns an Express-style middleware: drop it in front of a handler.
const gate = requirePayment({ chain: 'base', token: 'USDC', amount: '0.10', payTo: '0xYourWallet' })


// PAY (agent side) — a fetch that pays 402s itself.
const client = new PipRailClient({ chain: 'base', wallet: { privateKey: process.env.AGENT_KEY } })


const res = await client.fetch('https://api.example.com/report') // pays the 402, then returns the page
const report = await res.json()

The same app can both take payments (gate) and make them (client). From here, PipRailClient is the buyer’s whole surface — quote, estimateCost, planPayment, and fetch.

Where to go next

Section titled “Where to go next”