The "Expertise Topic" input box on the Android App has a limit of about 24 characters whereas the same input box on the Windows App allows for far more.
Personally I like having more space but it does make sense to limit this to one sentence. Perhaps 120 characters or so.
Thank you for brining this inconsistency to our attention.
The purpose of the Expertise field is really to facilitate finding the expert. So think of it more like # tags. To provide more information about your expertise, please update the summary field in your profile.
This is not a use case we considered. Thanks for bringing it to our attention. We'll explore ways to make this convenient, possibly by introducing caller restrictions (which will be a more concrete way of constraining who can call).