Seems rude to call in Michael to clear the space and then ask him to leave afterwards lol
In ceremonial magick, a spirit’s identity is usually verified by asking it to state its name, and to draw its seal. According to tradition, it is a quirk of this universe that a spirit can only speak its own name if commanded to identify itself, and can only draw its own seal. A parasite or impostor will most often use titles or equivocate, saying things like “You know who I am,” or “I am the Morningstar,” without actually stating their name.
Your evocation was non traditional though, so I don’t know if that “quirk” actually holds without any sort of binding.
Fortunately, we have something here that will solve the issue. Draw out this seal and use it along with Lucifer’s seal when you next call him. It will take care of it if it’s an impostor as well as answer your question.