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POST
/
swap
/
usdc-e
/
build
Build USDC → USDC.e swap
curl --request POST \
  --url https://relayer.kuest.com/swap/usdc-e/build \
  --header 'Content-Type: application/json' \
  --data '
{
  "from": "0x0B2B3E6B323C0Cd7bEaf4B7cC73b983D4E9B12c7",
  "proxyWallet": "0x3f8Be6FC21f4a5127A42CE1aF58d8bCb8A94F3c1",
  "amount": "1000000",
  "slippageBps": 50
}
'
{
  "nonce": "12",
  "transaction": {
    "to": "0xA238CBeb142c10Ef7Ad8442C6D1f9E89e07e7761",
    "value": "0",
    "data": "0x8d80ff0a0000000000000000000000000000000000000000000000000000000000000040",
    "operation": 1
  },
  "signatureParams": {
    "operation": "1",
    "safeTxnGas": "0",
    "baseGas": "0",
    "gasPrice": "0",
    "gasToken": "0x0000000000000000000000000000000000000000",
    "refundReceiver": "0x0000000000000000000000000000000000000000"
  },
  "amountIn": "1000000",
  "amountOutMinimum": "999000",
  "fee": 100,
  "deadline": 1711990000
}
Build a Safe multisend payload that approves native USDC and swaps it into USDC.e using Uniswap V3. The response includes the Safe transaction, nonce, and signatureParams required for signing.
POST to https://relayer.kuest.com/swap/usdc-e/build with the standard L2 headers. The relayer validates that from matches the authenticated account and that the Safe proxy is registered.

​
Request body

FieldTypeRequiredDescription
fromstringYesSafe owner address that must match KUEST_ADDRESS.
proxyWalletstringYesSafe proxy that will execute the swap.
amountstringYesUSDC amount in base units (6 decimals). Example: 1000000 = 1 USDC.
slippageBpsnumberNoSlippage tolerance in basis points. Default: 50 (0.5%).

​
Response fields

FieldTypeDescription
noncestringSafe nonce that must be signed.
transactionobjectSafe transaction payload pointing to the Safe multisend contract.
signatureParamsobjectGas + refund params to include in the Safe signature payload.
amountInstringEcho of the input amount (base units).
amountOutMinimumstringMinimum USDC.e out after slippage.
feenumberUniswap V3 pool fee selected (e.g. 100 = 0.01%).
deadlinenumberUnix timestamp deadline used in the swap call.
Use the returned transaction, nonce, and signatureParams to build the Safe typed data and produce the signature you will send to /swap/usdc-e/submit.

Body

application/json

Request payload for building a USDC → USDC.e swap multisend.

​
from
string
required

Safe owner address that must match the authenticated account.

​
proxyWallet
string
required

Safe proxy that will execute the swap.

​
amount
string
required

USDC amount in base units (6 decimals).

​
slippageBps
integer<int32>

Optional slippage tolerance in basis points.

Response

Swap payload built and ready for signing.

Built swap payload plus quote metadata.

​
nonce
string
required
​
transaction
object
required

Safe transaction payload returned by swap build endpoints.

​
signatureParams
object
required
​
amountIn
string
required
​
amountOutMinimum
string
required
​
fee
integer<int32>
required
​
deadline
integer<int64>
required