curl --request GET \
  --url https://api-sandbox.circle.com/v1/businessAccount/balances \
  --header 'Authorization: Bearer <token>'

{
  "data": {
    "available": [
      {
        "amount": "3.14",
        "currency": "USD"
      }
    ],
    "unsettled": [
      {
        "amount": "3.14",
        "currency": "USD"
      }
    ]
  }
}