@piprail/sdk

Accept and make x402 crypto payments — on any EVM chain plus Solana, TON, Tron, NEAR, Sui, Aptos, Algorand, Stellar & the XRP Ledger — in a couple of lines.

No middleman, no database, no fee, no account. Payments settle straight into your wallet, verified locally against your own RPC. Gate a route to make it paid-only; point an agent at a paid URL and it pays itself.

npm install @piprail/sdk viem

📖 Full documentation → docs.piprail.com

The docs are the single, searchable source of truth — every function, option, chain, and example, plus the MCP server, spend controls, discovery, and the complete error model. This README is just the front door.

Charge for an endpoint

import { requirePayment } from '@piprail/sdk'

app.get('/report',
  requirePayment({ chain: 'base', token: 'USDC', amount: '0.05', payTo: '0xYourWallet…' }),
  (_req, res) => res.json({ report: 'TOP SECRET' }),
)

That route now costs 0.05 USDC on Base, paid straight to your wallet. One parameter picks the chain. → Accepting payments

Let an agent pay for it

import { PipRailClient } from '@piprail/sdk'

const client = new PipRailClient({ chain: 'base', wallet: { key: process.env.AGENT_KEY } })

const res = await client.fetch('https://api.example.com/report') // hits the 402, pays it, retries with proof

Pay across chains — one buyer, a wallet per chain

A client is bound to one chain (an EVM key can't sign a Solana tx). To pay a 402 on whatever chain it asks for, give a MultiChainPayer one wallet per chain — it surveys every chain you hold and pays the first one you listed that can settle (your preference; within a chain, the cheapest-gas rail — there's no oracle to compare gas across coins):

import { MultiChainPayer } from '@piprail/sdk'

const payer = MultiChainPayer.fromWallets({
  wallets: {
    base:   { key: process.env.EVM_KEY },     // one EVM key works on every EVM chain
    solana: { key: process.env.SOLANA_KEY },
    xrpl:   { key: process.env.XRPL_SEED },
  },
  policy: { maxAmount: '1.00', maxTotal: '10.00', tokens: ['USDC', 'USDT'] }, // one budget, every chain
})

await payer.planPayment(url) // read-only: every chain ranked, payable-first in your listed order
const res = await payer.get(url) // pays on the first chain that can settle — same spend policy, no manual routing

Built on planAcross / fetchAcross (the same composable primitives, for when you already hold an array of clients). See examples/multi-chain.

The same app can take payments and make them. → Making payments

Documentation

| | | |---|---| | Getting started | Install · quickstart · how it works | | Accepting payments | requirePayment · createPaymentGate · the exact rail | | Making payments | PipRailClient · quote · estimateCost · planPayment · auto-route · MultiChainPayer | | Spend controls | Budgets · time envelope · the spend ledger | | Agent toolkit | paymentTools · the agent guide · NL renderers | | Discovery | Find & be found on the open x402 indexes ($0, no backend) | | Chains & tokens | Every chain, per-family setup & caveats | | Errors | The complete typed error model | | MCP server | Give any AI agent a budget-bound wallet | | Reference | The complete API surface |

Spread the word

PipRail is free, open-source, and has no backend to sell you. If it saved you from building a payments backend, help other developers (and their agents) find it:

⭐ Star on GitHub  ·  𝕏 Follow @piprailhq  ·  🌐 piprail.com  ·  📖 docs.piprail.com

License & trademark

The code is MIT — use it, fork it, ship it. PipRail™, the logo, and the @piprail npm scope are trademarks of the PipRail project: build on the code freely, but please don't call a fork "PipRail" or imply it's official. See TRADEMARK.md.