Command line tool for interacting with Bluetooth Low Energy devices, similar to gatttool
GATT isn't exposed on macOS as easily as CoreBluetooth (which you can get to easily from the command line with swift or python and objective c bridging).


https://github.com/adafruit/Adafruit_Python_BluefruitLE/tree/master/Adafruit_BluefruitLE/corebluetooth
https://github.com/karulis/pybluez


The pybluez code is very well commented and has good nuggets like:


  See https://developer.apple.com/documentation/iobluetooth
  for Apple's IOBluetooth documentation.
  
  See http://pyobjc.sourceforge.net for details on how to access Objective-C
  classes through PyObjC.


If those python examples don't work, then if you are a developer, I would start with the Additional Tools downloads for Xcode (latest beta version). If you're not a developer, then the free Xcode would be where I start to see how quickly you could get to GATT or see if the CoreBluetooth API are suitable for what you want to do.