payment_queryFeeDetails - JSON-RPC Method

Returns a detailed breakdown of fee components for a signed extrinsic.

Parameters

Parameter	Type	Required	Description
extrinsic	string	Yes	SCALE-encoded signed extrinsic in hex

cURL Example

curl -X POST https://api-moonbase-alpha.n.dwellir.com/YOUR_API_KEY \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc":"2.0",
    "id":1,
    "method":"payment_queryFeeDetails",
    "params":["0x<signed_extrinsic_hex>"]
  }'

JavaScript (polkadot.js)

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

async function details(exHex: string) {
  const api = await ApiPromise.create({ provider: new WsProvider('wss://api-moonbase-alpha.n.dwellir.com/YOUR_API_KEY') });
  const d = await api.rpc.payment.queryFeeDetails(exHex);
  console.log(d.toHuman());
  await api.disconnect();
}

Returns

Includes inclusionFee and optional tip fields.

Notes

• Use after constructing the exact signed extrinsic to get precise costs.
• Pair with system_accountNextIndex to sign with the correct nonce.