NodeJS POST request returning bad json error, but is it?

I am trying to call Google NEST API for the thermastat, but im getting thw following error:

{
    "error": {
      "code": 400,
      "message": "Invalid JSON payload received. Unknown name "params[heatCelsius]": Cannot bind query parameter. Field 'params[heatCelsius]' could not be found in request message.",
      "status": "INVALID_ARGUMENT",
      "details": [
        {
          "@type": "type.googleapis.com/google.rpc.BadRequest",
          "fieldViolations": [
            {
              "description": "Invalid JSON payload received. Unknown name "params[heatCelsius]": Cannot bind query parameter. Field 'params[heatCelsius]' could not be found in request message."
            }
          ]
        }
      ]
    }
  }

Here is how I am creating the post data:

    var temp = req.query.temp;
    var coolOrHeat = req.query.coolHeat;

    let celsius = (temp - 32) * 5 / 9;

    var jsonDataObj;

    if (coolOrHeat == "heat") {
        jsonDataObj = {
            command: 'sdm.devices.commands.ThermostatTemperatureSetpoint.SetHeat',
            params: {
                heatCelsius: celsius
            }
        }
    }

    if (coolOrHeat == "cool") {
        jsonDataObj = {
            command: 'sdm.devices.commands.ThermostatTemperatureSetpoint.SetCool',
            params: {
                coolCelsius: celsius
            }
        }
    }

Here is my POST req

            var urlSetTemp = 'https://smartdevicemanagement.googleapis.com/v1/enterprises/' + projectId + '/devices/' + thermId + ':executeCommand';

            request.post({
                headers: {
                    'content-type': 'application/json',
                    'Authorization': 'Bearer ' + accessToken
                },
                form: jsonDataObj,
                url: urlSetTemp
            }, function (error, response, body) {

                var json = JSON.parse(body);
                console.log("res: ", json);


                res.json({
                    'json': json,
                    'ack': "success",
                    'body': jsonDataObj
                });
            });

Google’s doc: https://developers.google.com/nest/device-access/traits/device/thermostat-temperature-setpoint#setheat

Finally, in postman, im good, it works, but not in node.

What exactly am I doing wrong?