Contract calls

A CONTRACT_CALL transaction asks Fireblocks to sign and broadcast a call to a method on an EVM smart contract, using calldata that you encode yourself. This page shows how to encode the calldata and send the transaction, and it assumes you have already initialised a fireblocks client as described in Choose an interface.

Choose between a contract call and the Web3 Provider

Use a CONTRACT_CALL transaction when you want to call the Create Transaction endpoint directly from your own backend, with full control over the calldata and the destination. If you would rather keep using your existing development tools, such as Hardhat, Foundry or ethers.js, which send standard JSON-RPC requests, use the EVM Web3 Provider for JavaScript-based tools or the Local JSON-RPC for other languages. Interact with smart contracts compares the options in more detail.

Encode the calldata

The contractCallData value is the hex-encoded ABI payload for the method you want to call. You can build it with any ABI library, and the following example uses ethers v6 to encode an ERC-20 approve call with placeholder values.

TypeScript

import { Interface } from "ethers";

const erc20 = new Interface([
  "function approve(address spender, uint256 amount)",
]);

const contractCallData = erc20.encodeFunctionData("approve", [
  "<SPENDER_ADDRESS>",
  1000000n,
]);

Send the contract call

The transaction uses the CONTRACT_CALL operation and passes the encoded calldata in extraParameters.contractCallData. The destination is the contract, which can be a one-time address or a contract wallet that you have added to your allowlist, and the amount is "0" for a non-payable method. The examples use the Sepolia testnet asset ETH_TEST5, and the SDK examples pass the calldata encoded in the previous step as <ENCODED_CALLDATA_HEX>.

import { TransferPeerPathType, TransactionOperation } from "@fireblocks/ts-sdk";

const response = await fireblocks.transactions.createTransaction({
  transactionRequest: {
    operation: TransactionOperation.ContractCall,
    assetId: "ETH_TEST5",
    amount: "0", // Conditional - Use "0" for non-payable methods, or the amount of native asset to send to a payable method
    source: {
      type: TransferPeerPathType.VaultAccount,
      id: "<SOURCE_VAULT_ACCOUNT_ID>",
    },
    destination: {
      type: TransferPeerPathType.OneTimeAddress, // Conditional - Use TransferPeerPathType.Contract with a contract wallet ID for an allowlisted contract
      oneTimeAddress: { address: "<CONTRACT_ADDRESS>" },
    },
    extraParameters: {
      contractCallData, // Required - Hex-encoded calldata from the previous step
    },
    note: "Approve spender", // Optional - Free-text note shown in your workspace, not sent to the blockchain
    externalTxId: "<YOUR_UNIQUE_ID>", // Optional - Your unique ID; Fireblocks rejects later requests with the same value
  },
});
console.log(response.data);

from fireblocks.models.transaction_request import TransactionRequest
from fireblocks.models.transaction_operation import TransactionOperation
from fireblocks.models.source_transfer_peer_path import SourceTransferPeerPath
from fireblocks.models.destination_transfer_peer_path import DestinationTransferPeerPath
from fireblocks.models.transfer_peer_path_type import TransferPeerPathType
from fireblocks.models.one_time_address import OneTimeAddress
from fireblocks.models.extra_parameters import ExtraParameters
from fireblocks.models.transaction_request_amount import TransactionRequestAmount

transaction_request = TransactionRequest(
    operation=TransactionOperation.CONTRACT_CALL,
    asset_id="ETH_TEST5",
    amount=TransactionRequestAmount("0"),  # Conditional - Use "0" for non-payable methods, or the amount of native asset to send to a payable method
    source=SourceTransferPeerPath(
        type=TransferPeerPathType.VAULT_ACCOUNT,
        id="<SOURCE_VAULT_ACCOUNT_ID>",
    ),
    destination=DestinationTransferPeerPath(
        type=TransferPeerPathType.ONE_TIME_ADDRESS,  # Conditional - Use TransferPeerPathType.CONTRACT with a contract wallet ID for an allowlisted contract
        one_time_address=OneTimeAddress(address="<CONTRACT_ADDRESS>"),
    ),
    extra_parameters=ExtraParameters(
        contract_call_data="<ENCODED_CALLDATA_HEX>",  # Required - Hex-encoded calldata from the previous step
    ),
    note="Approve spender",  # Optional - Free-text note shown in your workspace, not sent to the blockchain
    external_tx_id="<YOUR_UNIQUE_ID>",  # Optional - Your unique ID; Fireblocks rejects later requests with the same value
)

future = fireblocks.transactions.create_transaction(
    transaction_request=transaction_request,
)
print(future.result().data)  # create_transaction returns a Future

import com.fireblocks.sdk.model.*;

TransactionRequest transactionRequest = new TransactionRequest()
    .operation(TransactionOperation.CONTRACT_CALL)
    .assetId("ETH_TEST5")
    .amount(new TransactionRequestAmount("0")) // Conditional - Use "0" for non-payable methods, or the amount of native asset to send to a payable method
    .source(new SourceTransferPeerPath()
        .type(TransferPeerPathType.VAULT_ACCOUNT)
        .id("<SOURCE_VAULT_ACCOUNT_ID>"))
    .destination(new DestinationTransferPeerPath()
        .type(TransferPeerPathType.ONE_TIME_ADDRESS) // Conditional - Use TransferPeerPathType.CONTRACT with a contract wallet ID for an allowlisted contract
        .oneTimeAddress(new OneTimeAddress().address("<CONTRACT_ADDRESS>")))
    .extraParameters(new ExtraParameters()
        .contractCallData("<ENCODED_CALLDATA_HEX>")) // Required - Hex-encoded calldata from the previous step
    .note("Approve spender") // Optional - Free-text note shown in your workspace, not sent to the blockchain
    .externalTxId("<YOUR_UNIQUE_ID>"); // Optional - Your unique ID; Fireblocks rejects later requests with the same value

CreateTransactionResponse transaction = fireblocks.transactions()
    .createTransaction(
        transactionRequest,
        null, // Optional - xEndUserWalletId (UUID), only for end-user wallet operations
        null) // Optional - Not used for transactions; use externalTxId in the request body
    .get()
    .getData();
System.out.println(transaction);

POST /v1/transactions

{
  "operation": "CONTRACT_CALL",
  "assetId": "ETH_TEST5",
  "amount": "0",
  "source": { "type": "VAULT_ACCOUNT", "id": "<SOURCE_VAULT_ACCOUNT_ID>" },
  "destination": {
    "type": "ONE_TIME_ADDRESS",
    "oneTimeAddress": { "address": "<CONTRACT_ADDRESS>" }
  },
  "extraParameters": { "contractCallData": "<ENCODED_CALLDATA_HEX>" },
  "note": "Approve spender",
  "externalTxId": "<YOUR_UNIQUE_ID>"
}

Sign the request with a JWT; see Signing a request.

# Preview the request without sending it
fireblocks transactions create-transaction \
  --data '{"operation":"CONTRACT_CALL","assetId":"ETH_TEST5","amount":"0","source":{"type":"VAULT_ACCOUNT","id":"<SOURCE_VAULT_ACCOUNT_ID>"},"destination":{"type":"ONE_TIME_ADDRESS","oneTimeAddress":{"address":"<CONTRACT_ADDRESS>"}},"extraParameters":{"contractCallData":"<ENCODED_CALLDATA_HEX>"},"externalTxId":"<YOUR_UNIQUE_ID>"}' \
  --dry-run

# Execute
fireblocks transactions create-transaction \
  --data '{"operation":"CONTRACT_CALL","assetId":"ETH_TEST5","amount":"0","source":{"type":"VAULT_ACCOUNT","id":"<SOURCE_VAULT_ACCOUNT_ID>"},"destination":{"type":"ONE_TIME_ADDRESS","oneTimeAddress":{"address":"<CONTRACT_ADDRESS>"}},"extraParameters":{"contractCallData":"<ENCODED_CALLDATA_HEX>"},"externalTxId":"<YOUR_UNIQUE_ID>"}' \
  --no-confirm

The contractCallData field cannot be combined with rawMessageData or inputsSelection in the same request, and the full request schema is on the Create Transaction reference page. To retry a request safely, set a unique externalTxId on every request, as described in Transaction idempotency.

Read the results of a contract call

Once the transaction completes, the response from the contract is available in the networkRecords of the transaction, which is described in Interpret contract call results with networkRecords.

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Key Link

Choose between a contract call and the Web3 Provider

Encode the calldata

Send the contract call

Read the results of a contract call

​Choose between a contract call and the Web3 Provider

​Encode the calldata

​Send the contract call

​Read the results of a contract call

Choose between a contract call and the Web3 Provider

Encode the calldata

Send the contract call

Read the results of a contract call