curl --request GET \
  --url https://synthesis.trade/api/v1/wallet/pol/{wallet_id}/balance \
  --header 'X-API-KEY: <api-key>'

{
  "success": true,
  "response": {
    "wallet_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    "chain_id": "POL",
    "address": "0x1234567890abcdef1234567890abcdef12345678",
    "balance": {
      "USDC.e": "1000.000",
      "USDC": "500.000"
    }
  }
}