It's pretty good for self improvement. I scored kinda high on neuroticism but after learning some psychology stuff like mindfulness/meditation/neuroplasticity/stoicism/ACT i managed to reduce it significantly after about 2.5 years. there was even a study recently that showed how using a app to change your personality and it's not easy and require serious training like learning a language or a musical instrument. I hope we will get eventually some open source version of that app.
and of course you need to be open to it, humans have a documented bias toward not believing what might hurt there self esteem.