@Algot the closeset I can think of that isn't a noun is "drive", eg "driving users to use it" or whatever. but i need it in the form of a noun. the definition "invocation" in that form i fear is a bit too muddy (e.g. as an entreaty)
Sounds like you're looking for something evoking "attractiveness" or "desire" to open/use...sort of like the near-obsessive urge to check to see if a new fediverse notification has come for me!
I do like that better than "engagement".
You could talk about intrinsic motivation to open the app because of its potential to meet a perceived need/desire.
Server run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!