Send a transaction

Basic payment

import { parseEther } from "viem";

const hash = await walletClient.sendTransaction({
  account,
  chain: walletClient.chain,
  to: recipient,
  value: parseEther("1.50"), // native USDC: 18 decimals
});

Calling your contract

const hash = await walletClient.writeContract({
  account,
  chain: walletClient.chain,
  address: CONTRACT,
  abi,
  functionName: "pay",
  args: [orderId],
  value: parseEther("1.50"),
});

What happens

1. CrackPay checks the call against your app's listing. If it is not allowed, the call rejects with 4100 and the user sees nothing.
2. CrackPay shows the user the amount and where it goes.
3. The user approves with their passkey.
4. CrackPay sends it with gas sponsored and waits for it to land.
5. The promise resolves with the transaction hash. The payment is final.

Request fields

Field	Behaviour
to	Required. No contract creation. The zero address is refused.
data	Optional
value	Optional. Native USDC, 18 decimals.
gas, gasPrice, maxFeePerGas, maxPriorityFeePerGas, nonce	Ignored

One call per transaction. There is no batching.

Tokens

For EURC, or any contract that pulls tokens with transferFrom, send two transactions and await each:

import { tokens } from "@crackpay/miniapp-sdk";
import { erc20Abi, parseUnits } from "viem";

const amount = parseUnits("5", tokens.EURC.decimals);

await walletClient.writeContract({
  account,
  chain: walletClient.chain,
  address: tokens.EURC.address,
  abi: erc20Abi,
  functionName: "approve",
  args: [CONTRACT, amount], // the exact amount, never unlimited
});

await walletClient.writeContract({
  account,
  chain: walletClient.chain,
  address: CONTRACT,
  abi,
  functionName: "payWithToken",
  args: [tokens.EURC.address, amount],
});

What a listed app may call

Call	Listed app	Test app
A contract in its listing	Allowed	Allowed
Any other contract or address	Refused, 4100	Allowed
approve on a listed token, spender in the listing	Allowed	Allowed
approve to any other spender	Refused, 4100	Allowed
transfer or transferFrom on a token	Refused, 4100	Allowed

Move tokens through your own contract, never with a direct token transfer.

Gas

CrackPay sponsors every transaction. Do not estimate gas, set fee fields, or keep a gas reserve in the user's balance.

:::note While Circle's sponsorship is paused When Circle Gas Station is unavailable, CrackPay falls back to the user's account paying its own fee, about a cent in USDC, and shows it in the confirmation. Your app still sets nothing. A payment of the user's entire balance can then fail for lack of the fee; CrackPay checks this before the passkey prompt. :::

Errors

See Error codes. Treat 4001 as a cancel.