> ## Documentation Index
> Fetch the complete documentation index at: https://base-a060aa97-eb-mini-app-ia-overhaul.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# buildSwapTransaction

The `buildSwapTransaction` function is used to get an unsigned transaction for a swap between two Tokens.

Before using this function, make sure to obtain a [Client API Key](https://portal.cdp.coinbase.com/projects/api-keys/client-key) from Coinbase Developer Platform.

{/* ## Usage */}

{/* <CodeGroup>
```tsx code
import { setOnchainKitConfig } from '@coinbase/onchainkit';
import { buildSwapTransaction } from '@coinbase/onchainkit/api';
import type { Token } from '@coinbase/onchainkit/token';

setOnchainKitConfig({ apiKey: 'YOUR_API_KEY' });

const fromToken: Token = {
name: 'ETH',
address: '',
symbol: 'ETH',
decimals: 18,
image: 'https://wallet-api-production.s3.amazonaws.com/uploads/tokens/eth_288.png',
chainId: 8453,
};

const toToken: Token = {
name: 'USDC',
address: '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913',
symbol: 'USDC',
decimals: 6,
image:
  'https://d3r81g40ycuhqg.cloudfront.net/wallet/wais/44/2b/442b80bd16af0c0d9b22e03a16753823fe826e5bfd457292b55fa0ba8c1ba213-ZWUzYjJmZGUtMDYxNy00NDcyLTg0NjQtMWI4OGEwYjBiODE2',
chainId: 8453,
};

const response = await buildSwapTransaction({
fromAddress: '0x...',
from: fromToken,
to: toToken,
amount: '0.1',
useAggregator: false,
});
```

```json return value
{
"approveTransaction": {
  "chainId": 8453,
  "data": "",
  "gas": 0,
  "to": "",
  "value": 0
},
"fee": {
  "baseAsset": {
    "name": "USDC",
    "address": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
    "currencyCode": "USDC",
    "decimals": 6,
    "imageURL": "https://d3r81g40ycuhqg.cloudfront.net/wallet/wais/44/2b/442b80bd16af0c0d9b22e03a16753823fe826e5bfd457292b55fa0ba8c1ba213-ZWUzYjJmZGUtMDYxNy00NDcyLTg0NjQtMWI4OGEwYjBiODE2",
    "blockchain": "eth",
    "aggregators": [Array],
    "swappable": true,
    "unverified": false,
    "chainId": 8453
  },
  "percentage": "1",
  "amount": "3517825"
},
"quote": {
  "from": {
    "address": "",
    "chainId": 8453,
    "decimals": 18,
    "image": "https://wallet-api-production.s3.amazonaws.com/uploads/tokens/eth_288.png",
    "name": "ETH",
    "symbol": "ETH"
  },
  "to": {
    "address": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
    "chainId": 8453,
    "decimals": 6,
    "image": "https://d3r81g40ycuhqg.cloudfront.net/wallet/wais/44/2b/442b80bd16af0c0d9b22e03a16753823fe826e5bfd457292b55fa0ba8c1ba213-ZWUzYjJmZGUtMDYxNy00NDcyLTg0NjQtMWI4OGEwYjBiODE2",
    "name": "USDC",
    "symbol": "USDC"
  },
  "fromAmount": "100000000000000000",
  "toAmount": "348264739",
  "amountReference": "from",
  "priceImpact": "",
  "chainId": 8453,
  "highPriceImpact": false,
  "slippage": "3",
  "warning": {
    "type": "warning",
    "message": "This transaction has a very high likelihood of failing if submitted",
    "description": "failed with 500000000 gas: insufficient funds for gas * price + value: address 0x4ed4E862860beD51a9570b96d89aF5E1B0Efefed have 0 want 100000000000000000"
  }
},
"transaction": {
  "chainId": 8453,
  "data": "0x...",
  "gas": 419661,
  "to": "0xdef1c0ded9bec7f1a1670819833240f027b25eff",
  "value": 100000000000000000
},
"warning": {
  "type": "warning",
  "message": "This transaction has a very high likelihood of failing if submitted",
  "description": "failed with 500000000 gas: insufficient funds for gas * price + value: address 0x4ed4E862860beD51a9570b96d89aF5E1B0Efefed have 0 want 100000000000000000"
}
}
```
</CodeGroup> */}

## Returns

[`Promise<BuildSwapTransactionResponse>`](/onchainkit/api/types#buildswaptransactionresponse)

## Parameters

[`BuildSwapTransactionParams`](/onchainkit/api/types#buildswaptransactionparams)

## Types

* [`BuildSwapTransactionResponse`](/onchainkit/api/types#buildswaptransactionresponse)
* [`BuildSwapTransactionParams`](/onchainkit/api/types#buildswaptransactionparams)