Piprail
@piprail
PipRail — a budget-bound x402 wallet for AI agents
PipRail is an MCP server that hands any AI agent — Claude Desktop, Cursor, Claude Code, Windsurf, VS Code, Cline — a budget-capped wallet to pay x402 ("402 Payment Required") payment-gated URLs on its own. It runs locally with your wallet and a spend policy the model cannot exceed — no backend, no custody, no facilitator, no fee.
Five tools
- piprail_discover — find payable x402 APIs on the open indexes (the phone book; no paying)
- piprail_quote_payment — price a gated URL without paying
- piprail_plan_payment — check it can pay (balance, gas, recipient-readiness) across every rail
- piprail_pay_request — fetch a URL, paying the 402 automatically within budget
- piprail_register — list an endpoint you run so other agents can find it
Quick start
npx -y @piprail/mcp — add the config block, set your wallet key + spend caps, restart your client.
Why it's safe
Every payment is checked against your spend policy (PIPRAIL_MAX_AMOUNT / PIPRAIL_MAX_TOTAL / PIPRAIL_TOKENS / PIPRAIL_HOSTS) — and against the token's true on-chain decimals — before any on-chain send. A lying merchant can't push a payment over the cap; an over-budget request is refused and nothing moves. Your key never leaves your machine.
Chains
Every major EVM chain plus Solana, TON, Tron, NEAR, Sui, Aptos, Algorand, Stellar, and the XRP Ledger — one PIPRAIL_CHAIN value picks everything. USDC almost everywhere, USDT on most, the native coin on all.
Links
- Setup guide: https://piprail.com/mcp
- npm: https://www.npmjs.com/package/@piprail/mcp
- MCP registry:
io.github.piprail/mcp - Source (MIT): https://github.com/piprail/piprail
Server Config
{
"mcpServers": {
"piprail": {
"command": "npx",
"args": [
"-y",
"@piprail/mcp"
],
"env": {
"PIPRAIL_PRIVATE_KEY": "<YOUR_WALLET_KEY>",
"PIPRAIL_CHAIN": "base",
"PIPRAIL_MAX_AMOUNT": "0.10",
"PIPRAIL_MAX_TOTAL": "10.00",
"PIPRAIL_TOKENS": "USDC"
}
}
}
}