eth_call - Moonriver RPC Method

Executes a new message call immediately without creating a transaction on Moonriver. Used for reading smart contract state.

Why Moonriver? Build on the Moonbeam canary network on Kusama for real-world testing of EVM dApps with Moonbeam code ships here first, full EVM compatibility on Kusama, 80% fee burn mechanism, and XCM cross-chain messaging.

When to Use This Method

The eth_call method serves these key scenarios for dApp developers testing on Kusama, early adopters, and teams requiring production-ready experimentation:

• Read smart contract state - Execute view and pure functions to query token balances, DeFi positions, and protocol data without spending gas
• Simulate transactions - Test contract interactions before submitting them on-chain, avoiding failed transactions and wasted gas costs
• Multi-call aggregator queries - Batch multiple read calls into a single request using multicall contracts, reducing API overhead on Moonriver
• MEV and arbitrage analysis - Simulate transaction bundles to evaluate profitable opportunities before execution on production-grade dApp testing, early feature deployment, and Kusama-based EVM applications

Common Use Cases

1. Read ERC20 Token Balance

Query an ERC20 token contract to retrieve the balance for a specific wallet address using the balanceOf(address) function selector encoded as calldata. The selector is derived from the first 4 bytes of keccak256("balanceOf(address)"), followed by the 32-byte zero-padded address argument.

import { JsonRpcProvider } from 'ethers';

const provider = new JsonRpcProvider('https://api-moonriver.n.dwellir.com/YOUR_API_KEY');
const tokenAddress = '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045';
const walletAddress = '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045';

const balanceSelector = '0x70a08231' + walletAddress.slice(2).padStart(64, '0');

async function getTokenBalance() {
  const result = await provider.call({
    to: tokenAddress,
    data: balanceSelector
  });
  console.log('Balance (raw):', BigInt(result).toString());
  return result;
}

getTokenBalance();

2. Query DeFi Protocol State

Read protocol reserves, price oracles, or user positions from DeFi contracts on Moonriver. Each protocol exposes view functions that let you inspect pool state without modifying it - ideal for building analytics dashboards and trading bots.

import { JsonRpcProvider, Interface } from 'ethers';

const provider = new JsonRpcProvider('https://api-moonriver.n.dwellir.com/YOUR_API_KEY');

const poolAbi = [
  'function getReserves() view returns (uint112 reserve0, uint112 reserve1, uint32 blockTimestamp)'
];
const poolInterface = new Interface(poolAbi);
const poolAddress = '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045';

async function getPoolReserves() {
  const data = poolInterface.encodeFunctionData('getReserves');
  const result = await provider.call({ to: poolAddress, data });
  const decoded = poolInterface.decodeFunctionResult('getReserves', result);
  console.log('Reserve 0:', decoded[0].toString());
  console.log('Reserve 1:', decoded[1].toString());
  return decoded;
}

getPoolReserves();

3. Simulate a Swap Before Execution

Before committing a token swap, call the router contract's quote function to calculate the expected output. This lets you validate slippage tolerance and compare rates across DEXes without risking gas on a failed trade.

import { JsonRpcProvider, Interface, parseEther } from 'ethers';

const provider = new JsonRpcProvider('https://api-moonriver.n.dwellir.com/YOUR_API_KEY');
const routerAddress = '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045';

const routerAbi = [
  'function getAmountsOut(uint amountIn, address[] calldata path) view returns (uint[] amounts)'
];
const routerInterface = new Interface(routerAbi);

async function simulateSwap(amountIn, tokenIn, tokenOut) {
  const data = routerInterface.encodeFunctionData('getAmountsOut', [
    parseEther(amountIn),
    [tokenIn, tokenOut]
  ]);
  const result = await provider.call({ to: routerAddress, data });
  const decoded = routerInterface.decodeFunctionResult('getAmountsOut', result);
  console.log('Expected output:', decoded[0][1].toString());
  return decoded[0][1];
}

simulateSwap('1.0', '0xTokenA...', '0xTokenB...');

Best Practices

• Use latest for current-state reads and pending for pre-confirmation simulation on Moonriver
• Encode function selectors correctly: take the first 4 bytes of the keccak256 hash of the function signature
• Handle revert errors gracefully by parsing the revert reason from the error response data
• For batch reads, use multicall contracts to combine multiple eth_call requests into a single RPC call
• eth_call does not consume gas, making it ideal for unlimited read queries on Moonriver

Code Examples

Error Handling

Related Methods

• eth_estimateGas - Estimate gas for transaction
• eth_sendRawTransaction - Send actual transaction