PipRail

MCP server · agent payments · 29 chains · local-only

An MCP server that lets Claude pay for things.

Hand any MCP client a budget-bound payment wallet. Claude Desktop, Cursor, Claude Code, Windsurf, VS Code, and Cline can pay x402-gated URLs on their own, across 29 chains, capped by a spend policy the model cannot exceed. No backend, no custody, no code. Writing code instead? Use the x402 SDK.

$ npx -y @piprail/mcp
@piprail/mcp on npm

Add it in one block.

Drop this into your MCP client with your wallet key and a budget. The defaults are deliberately small and safe: 0.10 per payment, 10.00 lifetime per token, USDC on Base.

claude_desktop_config.json 
// claude_desktop_config.json: paste, restart, done
{
  "mcpServers": {
    "piprail": {
      "command": "npx",
      "args": ["-y", "@piprail/mcp"],
      "env": {
        "PIPRAIL_PRIVATE_KEY": "0x…",
        "PIPRAIL_CHAIN": "base",
        "PIPRAIL_MAX_AMOUNT": "0.10"
      }
    }
  }
}

Restart your client and the tools appear.

Never commit your key. Cursor, Claude Code, Windsurf and VS Code support ${env:PIPRAIL_PRIVATE_KEY} interpolation, so keep it out of the file. Claude Desktop takes the plain value, so treat that config as a secret.

Per-client config Every env var

Eight tools, the moment it connects.

A complete, safe payment workflow: discover → quote → plan → pay, then verify. Only piprail_pay_request moves money; the rest are read-only.

Budget-bound and local-only. The policy is enforced before any send, so the model can’t overspend even if it tries. On 14 chains the seller can offer a gasless rail, so the agent pays nothing but the price: which x402 facilitator settles where. Full tool reference →

Drop it into your framework.

First-party integrations give your agent a budget-bound wallet, most by wrapping this same MCP server (the native elizaOS plugin and n8n node use the SDK directly). No config wrangling.

OpenClaw logo

OpenClaw

ClawHub skill

Hand an OpenClaw agent a budget-bound wallet across every major chain. Install the ClawHub skill or add one mcp.servers entry and the eight piprail_* tools appear, capped by a spend policy.

clawhub install piprail
Set it up
Hermes logo

Hermes

Native MCP

Hand a Hermes agent a budget-bound wallet across every major chain. One command and the eight piprail_* tools appear. No facilitator, no fee, capped by a spend policy.

hermes mcp add piprail --command npx --args -y @piprail/mcp
Set it up
elizaOS logo

elizaOS

Native plugin

Hand an elizaOS agent a budget-bound wallet across every major chain. Add one plugin and it gets six native payment actions (pay, quote, plan, discover, budget, guide). No facilitator, no fee, capped by a spend policy.

npm i @piprail/elizaos-plugin
Set it up
n8n logo

n8n

Community node

Pay x402 URLs from any n8n workflow. Install one community node and a PipRail node appears with four operations (pay, plan, quote, estimate cost) callable by n8n AI Agent nodes and capped by a spend policy. EVM chains, no facilitator, no fee.

@piprail/n8n-nodes-piprail
Set it up
Mastra logo

Mastra

MCP server

The first x402 payment integration for Mastra. Wire @piprail/mcp in through Mastra's MCPClient and an agent gets all eight PipRail tools (pay, plan, quote, discover, budget and more) capped by a spend policy. Every chain, no facilitator, no fee.

npx -y @piprail/mcp
Set it up
More coming Vercel AI SDKCrewAI

Building on a framework that isn’t here yet? It already works as a raw MCP server. All integrations →

Why it's safe.

The spend policy is the boundary, and it's enforced where it counts.

Caps enforced before any send

Per-call and lifetime-per-token limits are checked against the token's true on-chain decimals, so a server can't understate a price to slip past a cap. Over budget → declined, nothing moves.

No custody, no backend

Runs locally with your key, your RPC, your limits. Payments settle wallet-to-wallet. PipRail holds nothing and runs no service. Nothing to compromise.

Open and auditable

MIT-licensed and open source: read it, audit it, run it yourself. No key ever leaves your machine.

Pay across all 29 chains: 20 EVM mainnets plus Solana, TON, Tron, NEAR, Sui, Aptos, Algorand, Stellar, and the XRP Ledger. See every chain →

MCP FAQ.

The trust questions, answered. The setup how-to lives in the docs.

How does spend budgeting work, and can the agent overspend?

No. PIPRAIL_MAX_AMOUNT caps each individual payment and PIPRAIL_MAX_TOTAL caps lifetime spend per token. Both are enforced by the SDK before any on-chain send, and checked against the token’s true on-chain decimals, so a malicious server can’t slip past a limit by misstating the price. An over-budget request comes back as { declined: true, reason } and nothing moves. You can also restrict tokens (PIPRAIL_TOKENS) and destination hosts (PIPRAIL_HOSTS).

How do I give Claude Desktop a spending-capped crypto wallet?

Add @piprail/mcp to your MCP config with a wallet key, a chain, and your caps: PIPRAIL_MAX_AMOUNT for the per-payment ceiling and PIPRAIL_MAX_TOTAL for lifetime spend. Claude Desktop then has a wallet it can spend from autonomously and cannot exceed, because the policy is enforced by the SDK before any on-chain send, not by asking the model to behave. Nothing is hosted: the server runs locally, the key stays on your machine, and payments go wallet-to-wallet with no custodian and no PipRail account. The same block works in Cursor, Claude Code, Windsurf, VS Code and Cline.

How do I set a budget limit on an AI agent that spends money?

PipRail enforces the limit in code, below the model, so a looping or jailbroken agent cannot talk its way past it. You get a per-payment cap (PIPRAIL_MAX_AMOUNT), a lifetime cap per token (PIPRAIL_MAX_TOTAL), a cross-token grand total by denomination (PIPRAIL_MAX_TOTAL_DENOM, e.g. USD:20.00), rolling-window caps on both spend and payment count (PIPRAIL_WINDOW_SECONDS with PIPRAIL_WINDOW_TOTAL and PIPRAIL_MAX_PAYMENTS_PER_WINDOW), plus token, chain and host allowlists. Set PIPRAIL_CONFIRM to require a human to approve each payment where the client supports elicitation, PIPRAIL_WARN_AT_FRACTION to be warned as a cap approaches, and PIPRAIL_SPEND_LOG to keep the budget durable across restarts. An over-budget request returns { declined: true, reason } and nothing moves.

Does the MCP take custody of my funds or run a backend?

No. The server runs locally on your machine with your key, your RPC, and your limits. Payments settle wallet-to-wallet straight to the recipient. PipRail runs no service and holds nothing. There’s no PipRail backend to compromise and no facilitator in the path. The server code is MIT and open; you can audit or run it yourself.

Which AI clients and chains does the MCP support?

Clients: Claude Desktop, Cursor, Claude Code, Windsurf, VS Code, and Cline, or any MCP client. Chains: all 29 PipRail supports, meaning 20 EVM mainnets plus Solana, TON, Tron, NEAR, Sui, Aptos, Algorand, Stellar, and the XRP Ledger. EVM works out of the box (the server ships with viem); non-EVM chains pull their SDK peer library on demand. Each server instance is one wallet on one chain, so register it once per chain to give an agent several rails.

What’s the difference between @piprail/sdk and @piprail/mcp?

The SDK is for developers who write code: you call requirePayment / createPaymentGate to charge, or PipRailClient to pay, in TypeScript. The MCP flips that: you write no code, you add an env block, and agents in your MCP client pay x402 URLs autonomously, capped by a spend policy. Same engine, same 29 chains, same backendless self-custody. The MCP is the zero-integration path for AI/agent operators.

Give your agent a wallet.

One env block, budget-bound, on every chain that matters.

npm install GitHub Read the docs