I figured it out, turns out I need to pass raw text instead of JSON for the params
IE:
{ "acctId": "12345", "conid": 346577750, "secType": "FUT", "cOID": "test003", "orderType": "MKT", "listingExchange": "GLOBEX", "outsideRTH": false, "side": "BUY", "price": 7000, "ticker": "NQ", "tif": "GTC"...