Build USDC transfer authorization

Build the EIP-3009 transferWithAuthorization typed data for a gasless USDC transfer on Base/Polygon/Arbitrum/Optimism/Ethereum/Monad/Celo/Avalanche/Sei - the exact EIP-712 object an agent signs with its OWN key to authorize an x402 payment. Send POST /api/transfer-authorization with the required fields from, to and amount and pay $0.003 per call over x402 or MPP (there is no free tier). It returns a JSON object with typedData and network.

We construct it; we never sign or send. Non-custodial.

Category: Payments & x402 · Tags: x402 eip-3009 eip-712 usdc transfer authorization gasless multichain

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Parameters

Example request

curl -i -X POST https://agent402.tools/api/transfer-authorization \
  -H "Content-Type: application/json" \
  -d '{"from":"0x1111111111111111111111111111111111111111","to":"0x2222222222222222222222222222222222222222","amount":0.01,"network":"base"}'

Without payment this returns HTTP 402 Payment Required with the exact price for transfer-authorization; any x402 v2 or MPP client pays it and retries.

Example response

{
  "typedData": {
    "domain": {
      "name": "USD Coin",
      "version": "2",
      "chainId": 8453,
      "verifyingContract": "0x833589f…"
    },
    "primaryType": "TransferWithAuthorization",
    "message": {}
  },
  "network": "base"
}

From an MCP client

catalog.call {
  "slug": "transfer-authorization",
  "params": {
    "from": "0x1111111111111111111111111111111111111111",
    "to": "0x2222222222222222222222222222222222222222",
    "amount": 0.01,
    "network": "base"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for transfer-authorization; the stdio package pays it from a wallet or from AGENT402_CREDITS_KEY. Local install: npx -y agent402-mcp.

Errors and behavior

• from, to and amount are required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged over x402, MPP or a prepaid credits key: settlement is cancelled when the tool fails. The exception is a Tempo push credential, a transfer the buyer sent before the call: it settles before the tool runs, so if the tool then fails the payment is recorded as a refund owed to the paying wallet.
• Wallet-only: this tool reaches the network or stored state, so it has no proof-of-work tier. A prepaid card-credits key issued earlier (Authorization: Bearer a402_...) also pays it.
• A GET or HEAD to /api/transfer-authorization returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again (an answer larger than 1 MB is not replayed).

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
client.setSpendControls?.(false); // keep your own spending ceiling in code
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/transfer-authorization", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "from": "0x1111111111111111111111111111111111111111",
    "to": "0x2222222222222222222222222222222222222222",
    "amount": 0.01,
    "network": "base"
  }),
});

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