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Documentation Index

Fetch the complete documentation index at: https://docs.arc.io/llms.txt

Use this file to discover all available pages before exploring further.

App Kit can provide an estimate of the fees you’ll incur before spending from a Unified Balance.

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Prerequisites

Before you begin, ensure that you’ve: These are required so any example below runs with a valid kit and adapter.

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Estimate fees before spending

This sample estimates then spends 1.00 USDC from Base Sepolia to Arc Testnet when you specify explicit amounts from a source blockchain:
For automatic routing (no explicit allocations), see Select source blockchains.
TypeScript
import { AppKit } from "@circle-fin/app-kit";
import { createViemAdapterFromPrivateKey } from "@circle-fin/adapter-viem-v2";

const kit = new AppKit();

const adapter = createViemAdapterFromPrivateKey({
  privateKey: process.env.EVM_PRIVATE_KEY as string,
});

const params = {
  amount: "1.00",
  from: {
    adapter,
    allocations: [{ amount: "1.00", chain: "Base_Sepolia" }],
  },
  to: {
    adapter,
    chain: "Arc_Testnet",
    recipientAddress: "0xRecipientAddress",
  },
};

const estimate = await kit.unifiedBalance.estimateSpend(params);
console.log("Estimated fees:", estimate.fees);

const result = await kit.unifiedBalance.spend(params);
Estimated fees may differ from actual fees due to network conditions at execution time. Review the estimate before proceeding.

​
Example fee response

The JSON below shows the shape of the fees array.
JSON
{
  "fees": [
    {
      "type": "provider",
      "token": "USDC",
      "amount": "0.00005",
      "allocations": [{ "chain": "Base Sepolia", "amount": "0.00005" }]
    },
    {
      "type": "gasFee",
      "token": "USDC",
      "amount": "3.311005",
      "allocations": [
        { "chain": "Ethereum Sepolia", "amount": "3.30" },
        { "chain": "Base Sepolia", "amount": "0.011005" }
      ]
    },
    {
      "type": "kit",
      "token": "USDC",
      "amount": ".1",
      "allocations": [{ "chain": "Ethereum Sepolia", "amount": ".1" }],
      "recipientAddress": "0x2222222222222222222222222222222222222222"
    }
  ]
}
Fee type values can include:
  • provider — Protocol transfer fee when the spend is crosschain. Not charged for same-chain spends.
  • gasFee — Onchain gas paid on source blockchains as part of the spend.
  • kit — Developer custom fee from your custom fee policy.
  • forwarder — Forwarding Service fee when the spend uses the forwarder (not shown in the sample above).
See How Unified Balance fees work for a conceptual fee breakdown.