How do UX demands arrive so they can work?

Here at the company, the demands come to the UXs in a very disorganized way. Sometimes they send it by e-mail, other times by chat, or sometimes they just send a look at the roadmap, which always only has the name of the feature without any details.

This is bad because we never have business specifications, or well-defined scopes, which creates problems when it comes to developing solutions.

I would like to know if there is any model that I can study to suggest here in the company.

Important: the context I mentioned is related to the implementation of features that have already been defined previously.