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payment_queryInfo - Hydration RPC Method

Estimate transaction fees on Hydration. Get the weight, dispatch class, and partial fee for an extrinsic before submitting it to the network.

Estimates the fee for an encoded extrinsic on Hydration. Returns the weight, dispatch class, and partial fee so you can display costs to users or verify sufficient balance before submitting transactions.

Why Hydration? Build on Polkadot's leading DEX with $200M+ TVL, Omnipool AMM, and native HOLLAR stablecoin with Omnipool with reduced slippage, permissioned listings, 3M DOT DAO allocation, and 200%+ APR farm yields.

When to Use This Method

payment_queryInfo is essential for DeFi developers, liquidity providers, and DAOs requiring capital-efficient trading:

  • Fee Display -- Show users the estimated transaction cost before they sign on Hydration
  • Balance Validation -- Verify the sender has sufficient funds to cover the fee plus the transfer amount for single-sided liquidity provision, cross-chain trading (SOL, KSM, tBTC), and HOLLAR decentralized stablecoin
  • Transaction Planning -- Compare fees across different extrinsic types to optimize costs
  • Batch Cost Estimation -- Estimate the total cost of batch transactions before submission

Code Examples

Common Use Cases

1. Pre-Transaction Fee Display

Show fees to users before they confirm a transaction:

JavaScript
import { ApiPromise, WsProvider } from '@polkadot/api';
import { BN } from '@polkadot/util';

async function displayFeeEstimate(api, extrinsic, senderAddress) {
  const [info, properties] = await Promise.all([
    extrinsic.paymentInfo(senderAddress),
    api.rpc.system.properties()
  ]);

  const decimals = properties.tokenDecimals.toJSON()[0];
  const symbol = properties.tokenSymbol.toJSON()[0];
  const fee = info.partialFee;

  // Convert to human-readable
  const divisor = new BN(10).pow(new BN(decimals));
  const whole = fee.div(divisor);
  const fractional = fee.mod(divisor).toString().padStart(decimals, '0');

  const formatted = `${whole}.${fractional.slice(0, 6)} ${symbol}`;
  console.log(`Estimated fee: ${formatted}`);
  console.log(`Dispatch class: ${info.class.toString()}`);

  return { fee: fee.toString(), formatted, class: info.class.toString() };
}

2. Sufficient Balance Check

Verify the sender can afford the transaction plus fees:

JavaScript
async function canAffordTransaction(api, senderAddress, recipient, amount) {
  const transfer = api.tx.balances.transferKeepAlive(recipient, amount);
  const [info, account] = await Promise.all([
    transfer.paymentInfo(senderAddress),
    api.query.system.account(senderAddress)
  ]);

  const fee = info.partialFee.toBigInt();
  const transferAmount = BigInt(amount);
  const totalCost = fee + transferAmount;
  const freeBalance = account.data.free.toBigInt();

  // Account for existential deposit
  const existentialDeposit = api.consts.balances.existentialDeposit.toBigInt();
  const available = freeBalance - existentialDeposit;

  const canAfford = available >= totalCost;

  console.log(`Free balance: ${freeBalance}`);
  console.log(`Total cost (amount + fee): ${totalCost}`);
  console.log(`Can afford: ${canAfford}`);

  return canAfford;
}

3. Compare Fees Across Transaction Types

Estimate fees for different operations to find the cheapest approach:

JavaScript
async function compareFees(api, sender) {
  const recipient = '5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY';
  const amount = 1000000000000;

  // Different transaction types
  const extrinsics = {
    'transfer': api.tx.balances.transferKeepAlive(recipient, amount),
    'transferAll': api.tx.balances.transferAll(recipient, false),
    'batchTransfer': api.tx.utility.batchAll([
      api.tx.balances.transferKeepAlive(recipient, amount / 2),
      api.tx.balances.transferKeepAlive(recipient, amount / 2)
    ])
  };

  const fees = {};
  for (const [name, ext] of Object.entries(extrinsics)) {
    const info = await ext.paymentInfo(sender);
    fees[name] = {
      partialFee: info.partialFee.toHuman(),
      weight: info.weight.toString(),
      class: info.class.toString()
    };
  }

  console.table(fees);
  return fees;
}

Error Handling

Common errors and solutions:

Error CodeDescriptionSolution
-32603Unable to query dispatch infoEnsure the extrinsic is properly encoded; verify it is a valid call for the current runtime
-32602Invalid paramsCheck the extrinsic hex is properly formatted with 0x prefix
-32005Rate limit exceededImplement client-side rate limiting or cache fee estimates for similar transactions
Execution errorRuntime unable to compute feeThe extrinsic may reference invalid pallets or calls; verify against current metadata

author_rotateKeys

Generate new session keys for validator operations on Hydration. Essential for validator setup, key rotation, and security best practices on Polkadot's leading DEX with $200M+ TVL, Omnipool AMM, and native HOLLAR stablecoin.

payment_queryFeeDetails

Get a detailed fee breakdown for an extrinsic on Hydration. Analyze base fee, length fee, and adjusted weight fee components to optimize transaction costs for single-sided liquidity provision, cross-chain trading (SOL, KSM, tBTC), and HOLLAR decentralized stablecoin.

On this page

When to Use This Method
Code Examples
Common Use Cases
1. Pre-Transaction Fee Display
2. Sufficient Balance Check
3. Compare Fees Across Transaction Types
Error Handling
Related Methods