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App Kit can estimate gas fees and provider fees before making a bridge transfer, and only proceed if the costs are acceptable.

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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 costs

This example estimates costs for a bridge transfer of 1.00 USDC from Ethereum Sepolia to Arc Testnet:
TypeScript
import type { BridgeParams } from "@circle-fin/app-kit";

const params: BridgeParams = {
  from: { adapter, chain: "Ethereum_Sepolia" },
  to: { adapter, chain: "Arc_Testnet" },
  amount: "1.00",
};

// Estimate costs
const estimate = await kit.estimateBridge(params);
console.log(
  `Estimating ${params.amount} USDC from ${params.from.chain} to ${params.to.chain}`,
);
console.log("Estimated fees:", estimate.fees);

const providerFee = estimate.fees.find(
  (fee) => fee.type === "provider",
)?.amount;

// Only proceed if the provider fee is less than 0.10 USDC
// Also proceed if the `providerFee` variable is null/undefined since there is no provider fee to charge
if (providerFee == null || parseFloat(providerFee) < 0.1) {
  // Execute the bridge transfer
  const result = await kit.bridge(params);
  console.log("Bridge transfer completed:", result);
} else {
  // Provider fee is 0.10 USDC or higher - abort the bridge transfer
  console.log("Provider fee is above threshold:", providerFee, "USDC");
}