As per ERC-4337, Paymasters facilitate transaction sponsorship, allowing third-party-designed mechanisms to pay for transactions. Many of these mechanisms could be done by having the paymaster wrap a UserOperation with their own, but there are some important fundamental limitations to that approach:
No possibility for “passive” paymasters (eg. that accept fees in some ERC-20 token at an exchange rate pulled from an on-chain DEX)
Paymasters run the risk of getting griefed, as users could send ops that appear to pay the paymaster but then change their behavior after a block
GET https://api.expand.network/aa/getpaymasterdata
| Name | Type | Description |
|---|---|---|
chainId
String
Refer to the Chain ID page for details.
chainSymbol
String
Refer to the Chain ID page for details.
sender*
String
On-chain wallet address.
rpc
String
Remote procedural call URL.
nonce
String
Anti-replay parameter.
initCode
String
The initCode of the account. (needed if and only if the account is not yet on-chain and needs to be created)
preVerificationGas
String
The amount of gas to pay for to compensate the bundler for pre-verification execution and calldata.
verificationGasLimit
String
The amount of gas to allocate for the verification step.
gasLimit
String
Maximum gas limit provided by the sender, for the transaction.
callGasLimit
String
The amount of gas to allocate the main execution call.
callData
String
Encoded data for executing the primary function call or operation within the user's transaction.
maxPriorityFeePerGas
String
Maximum priority fee per gas. (similar to EIP-1559 max_priority_fee_per_gas)
maxFeePerGas
String
The maximum fee per gas to pay for the execution of this operation. (similar to EIP-1559 max_fee_per_gas)
signature
String
Data passed into the account along with the nonce during the verification step.
paymasterAndData
String
Address of paymaster sponsoring the transaction, followed by extra data to send to the paymaster. (empty for self-sponsored transaction)
paymasterContractAddress*
String
Address of the contract from where, gas is to be paid.
mockValidAfter*
String
The UserOp is valid only after this time, to be sent in epoch time format.
mockValidUntil*
String
The UserOp is valid only up to this time, to be sent in epoch time format.