change metadata tag before importing mp4 into iTunes to Music Video I am a DJ and use record pools to download music and music videos. This is a legal source of mp3 and mp4 of music singles remixed/edited from the album version. 

My current workflow is:


Hazel will find mp3s that have not been matched before, open in Metadatics app and add a color tag.
Keyboard maestro when it detects Metadatics is open and execute macros emulating keystrokes to select all then strip all artwork then save all and finally quit metadatics.
Hazel will search for mp3s with color tag that are more than 30 minutes old and import into iTunes.


I want to run a similar workflow with mp4 that will 


match mp4s that contain source/URL of the record pool URL.  
strip artwork
change metadata so mp4 is imported as Music Video


TL;DR 
what is the metadata tag to make a mp4 imported into iTunes as Music Video?
If I recall correctly, music videos have the following metadata:


genre: Music Video
media kind Music Video
kind Purchased MPEG-4 video file


As a minimum, I imagine you'd have to change the genre and media kind metadata so that they're labelled as Music Video to ensure the .mp4 files are imported as music videos. 

As an aside, you can typically view the above metadata within iTunes by doing a Get Info. That is, select the item and press command I (or you can go to iTunes > Edit > Get Info). This brings up all the metadata and you can view the:


genre within the Details tab
media kind within the Options tab
kind within the File tab