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Home / Guides / Let your agent pay anyone: the non-custodial x402 payments toolkit

Let your agent pay anyone: the non-custodial x402 payments toolkit

An autonomous agent that can pay is far more useful than one that can't - but you don't want a middleman holding your money. Agent402's payments tools are non-custodial: they help an agent move its own USDC with its own key. Agent402 never holds, signs, or sends funds - it decodes quotes, reads public chain state, and builds the authorization you sign. Everything below works on Base, Polygon, Arbitrum, Optimism, Ethereum, and Robinhood Chain (network param, default base), and needs no API key.

1. What does this endpoint cost? - /api/x402-quote

Point it at any paid URL and get the decoded HTTP 402 terms:

curl "https://agent402.tools/api/x402-quote?url=https://api.example.com/paid&method=GET"
# { "status": 402, "paymentRequired": true,
#   "accepts": [{ "scheme":"exact","network":"base","asset":"USDC","maxAmountRequired":"1000","payTo":"0x…" }] }

2. Who am I paying? - /api/ens-resolve

Turn a human-readable name into a payable address:

curl "https://agent402.tools/api/ens-resolve?name=vitalik.eth"
# { "name":"vitalik.eth", "address":"0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045", "found":true }

3. Can I afford it? - /api/usdc-balance + /api/gas-estimate

curl "https://agent402.tools/api/usdc-balance?address=0xYOURWALLET&network=base"
# { "usdc":"12.5", "raw":"12500000", "network":"base" }
curl "https://agent402.tools/api/gas-estimate?network=base"
# { "gasPriceGwei":"0.0051", "network":"base" }

4. Build the authorization to sign - /api/transfer-authorization

This returns the exact EIP-3009 transferWithAuthorization typed data for a gasless USDC transfer. Agent402 builds it; your agent signs it locally:

curl -X POST https://agent402.tools/api/transfer-authorization \
  -H "Content-Type: application/json" \
  -d '{"from":"0xYOURWALLET","to":"0xRECIPIENT","amount":0.01,"network":"base"}'
# { "typedData": { "domain":{...}, "primaryType":"TransferWithAuthorization", "message":{...} }, ... }

Sign it with your own key - Agent402 never sees it:

import { privateKeyToAccount } from "viem/accounts";
const account = privateKeyToAccount(process.env.AGENT_KEY);
const { typedData } = await (await fetch("https://agent402.tools/api/transfer-authorization", {
  method: "POST", headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ from: account.address, to: recipient, amount: 0.01 }),
})).json();
const signature = await account.signTypedData(typedData); // submit to the facilitator / payTo's x402 flow

5. Did it settle? - /api/x402-verify

After a payment lands, confirm it on-chain - and optionally that it paid the right address at least a minimum amount:

curl "https://agent402.tools/api/x402-verify?hash=0xTXHASH&network=base&to=0xRECIPIENT&min=0.001"
# { "settled":true, "status":"success", "transfers":[{"from":"0x…","to":"0x…","usdc":"0.001"}], "matched":true }

Why non-custodial matters

Custodial "pay for me" services have to hold your funds - which means money transmission, KYC/AML, and trust in a middleman. These tools never touch your money: you keep your key, you sign, you send. That's the right architecture for agent payments, and it's the one Agent402 ships. The whole kit is open source and priced per call in USDC (or proof-of-work on the free tools).

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