PipRail

A self-custodial crypto payment wallet for your OpenClaw agent, with a hard spend cap it can't exceed. It autonomously pays x402 paywalls ('402 Payment Required') on every major chain, settling funds straight to the recipient — no facilitator, no fee, no signup. Runs read-only with no key (discover/quote/plan before you add a wallet); add a key only to let the agent pay, optionally gaslessly via the standard x402 'exact' rail.

PipRail — Agent Payment Wallet 🛤️

Give your OpenClaw agent a self-custodial crypto payment wallet with a hard spend cap it can't exceed. It autonomously pays x402 "402 Payment Required" paywalls across every major chain — settling funds straight to the recipient's wallet, with no facilitator, no fee, no signup.

No API key. No account. No signup. PipRail is self-custodial — you bring a wallet you control. It even runs read-only with zero config: discover, quote, register, budget, and guide work the moment it starts, no key at all. Add your own wallet key (PIPRAIL_PRIVATE_KEY) only when the agent should actually pay — it's a wallet signing key you hold, never an API credential, and it never leaves your machine.

PipRail plugs into OpenClaw as a standard MCP server — the published @piprail/mcp (npx -y @piprail/mcp) over stdio — so the agent gets all 8 tools natively, capped by a budget it can't exceed.

Why PipRail (vs every other crypto skill)

Every other OpenClaw payment skill routes through a facilitator or custodian that holds keys and/or takes a cut. PipRail is different:

• Backendless — no facilitator, no hosted service. Payments verify locally against your own RPC.
• No fee — funds settle straight to the service provider's wallet. PipRail takes nothing.
• Self-custodial — your key, your machine. PipRail hosts and holds nothing.
• Every major chain — EVM (Base, Ethereum, Polygon, Arbitrum, Optimism, Avalanche, BNB…), Solana, TON, Tron, NEAR, Sui, Aptos, Algorand, Stellar, XRPL — one PIPRAIL_CHAIN param picks everything.
• Gasless when you want it — opt into the standard x402 exact rail (PIPRAIL_SCHEMES=exact) and the agent pays zero gas: it signs the transfer (EIP-3009/Permit2 on EVM, SVM on Solana) and the server settles.
• A hard spend cap the model can't cross — PIPRAIL_MAX_TOTAL=5.00 and that's the ceiling, enforced in the SDK before any on-chain send. MIT open source.

The 8 tools your agent gets

Tool	What it does	Moves money?
piprail_discover	Find payable x402 APIs on the open indexes — filter by category/asset/reliability, sort by price or uptime	no
piprail_quote_payment	Get a URL's price without paying	no
piprail_plan_payment	Check you can afford it (balance + gas + recipient-ready)	no
piprail_pay_request	Pay the 402 and return the resource	yes
piprail_register	List your own x402 API so other agents find it — add a category + tags for findability	no
piprail_budget	Read remaining spend + time leash	no
piprail_guide	Read the agent contract (how to quote → plan → pay)	no
piprail_verify_receipt	Re-verify a payment receipt against the chain, wallet-free	no

Only piprail_pay_request moves funds. Six tools — discover, quote, register, budget, guide, verify_receipt — work with no key at all; pay and plan (it reads your balance) need your wallet.

Six more if you hand the agent its own wallet. Set PIPRAIL_MODE=sovereign (plus a required PIPRAIL_MAX_PER_SWAP) and it also gets piprail_quote_swap, piprail_swap, and the earning side: piprail_sell, piprail_collect, piprail_earnings and piprail_wallet. It appends to the table above rather than replacing it, so nothing changes unless you opt in. Receiving needs no key at all, which is why the agent can be paid on a machine that cannot spend. How the modes work.

Install

Discover + install on ClawHub (either command works):

bash

clawhub install piprail            # the ClawHub CLI
openclaw skills install piprail     # …or OpenClaw's native command

Then wire the MCP server into ~/.openclaw/openclaw.json — OpenClaw nests servers under mcp.servers. No key is needed — this is the whole config, and it starts the server read-only (discover / quote / register / budget / guide all work):

json

{ "mcp": { "servers": { "piprail": {
  "command": "npx", "args": ["-y", "@piprail/mcp"],
  "env": { "PIPRAIL_CHAIN": "base" }
} } } }

Want the agent to actually pay? Then — and only then — add your own self-custodial wallet key plus a budget cap (PIPRAIL_PRIVATE_KEY is a wallet signing key you hold, never an API key):

json

{ "mcp": { "servers": { "piprail": {
  "command": "npx", "args": ["-y", "@piprail/mcp"],
  "env": { "PIPRAIL_CHAIN": "base", "PIPRAIL_MAX_TOTAL": "5.00", "PIPRAIL_PRIVATE_KEY": "0xYOUR_KEY" }
} } } }

Restart OpenClaw (or run openclaw mcp set) and the piprail_* tools appear. See Configure below.

Configure

Variable	Required	Default	Purpose
PIPRAIL_PRIVATE_KEY	— (only to pay)	—	Your self-custodial wallet key/seed. Omit it for read-only (discover/quote/register/budget/guide); set it only to let the agent pay. Not an API key; never sent anywhere.
PIPRAIL_CHAIN	—	base	Which chain to pay on
PIPRAIL_CHAINS	—	—	Pay across several chains (instead of PIPRAIL_CHAIN) — e.g. base,polygon,solana; give each its own PIPRAIL_<CHAIN>_KEY. The agent pays whichever chain a 402 asks for (the first you listed that can settle), under one shared budget.
PIPRAIL_MAX_AMOUNT	—	0.10	Max per payment, in the token's units (≈ $ for USDC/USDT; native-coin units on a native rail)
PIPRAIL_MAX_TOTAL	—	10.00	Lifetime budget per (chain, token)
PIPRAIL_TOKENS	—	chain stables	Allowed tokens
PIPRAIL_SCHEMES	—	onchain-proof	Add exact to also pay standard x402 servers
PIPRAIL_RPC_URL	—	chain default	Custom RPC endpoint (recommended in production; fold any API key into the URL)

Defaults are deliberately small and safe (0.10 per payment, 10.00 lifetime, USDC on Base). Start there, raise as you trust it.

The agent workflow

discover → quote → plan → pay. A typical session:

text

User:  Find me a crypto price API I can pay for.
Agent: [piprail_discover("crypto price")]  → cheapest is 0.001 USDC/call on Base.
User:  Can I afford it?
Agent: [piprail_plan_payment(url)]  → yes; 4.82 USDC left of 5.00, recipient ready, gas ~$0.05.
User:  Get me the ETH price.
Agent: [piprail_pay_request(url)]  → paid 0.001 USDC (tx 0x…). ETH: $3,247.18. 4.819 USDC left.

Learn more

• Docs: docs.piprail.com/integrations/openclaw · the 8 tools · spend controls
• Source (MIT): github.com/piprail/piprail — ⭐ a star helps others find it
• Follow: @piprailhq on X — new chains, ship logs, agent-payment tips
• Live payable demo: piprail.com/x402/demo