curl --request GET \
  --url https://futures.kraken.com/derivatives/api/v3/accounts \
  --header 'APIKey: <api-key>' \
  --header 'Authent: <api-key>'

{
  "accounts": {
    "cash": {
      "balances": {
        "xbt": "141.31756797",
        "xrp": "52465.1254"
      },
      "type": "cashAccount"
    },
    "fi_xbtusd": {
      "auxiliary": {
        "af": 100.73891563,
        "funding": 100.73891563,
        "pnl": 12.42134766,
        "pv": 153.73891563,
        "usd": 0
      },
      "balances": {
        "xbt": "141.31756797"
      },
      "currency": "xbt",
      "marginRequirements": {
        "im": 52.8,
        "lt": 39.6,
        "mm": 23.76,
        "tt": 15.84
      },
      "triggerEstimates": {
        "im": 3110,
        "lt": 2890,
        "mm": 3000,
        "tt": 2830
      },
      "type": "marginAccount"
    },
    "flex": {
      "type": "multiCollateralMarginAccount",
      "currencies": {
        "XBT": {
          "quantity": 0.1185308247,
          "value": 4998.721054420551,
          "collateral": 4886.49976674881,
          "available": 0.1185308247
        },
        "USD": {
          "quantity": 5000,
          "value": 5000,
          "collateral": 5000,
          "available": 5000
        },
        "EUR": {
          "quantity": 4540.5837374453,
          "value": 4999.137289089901,
          "collateral": 4886.906656949836,
          "available": 4540.5837374453
        }
      },
      "balanceValue": 34995.52,
      "portfolioValue": 34995.52,
      "collateralValue": 34122.66,
      "initialMargin": 0,
      "initialMarginWithOrders": 0,
      "maintenanceMargin": 0,
      "pnl": 0,
      "unrealizedFunding": 0,
      "totalUnrealized": 0,
      "totalUnrealizedAsMargin": 0,
      "marginEquity": 34122.66,
      "availableMargin": 34122.66
    }
  },
  "result": "success",
  "serverTime": "2016-02-25T09:45:53.818Z"
}