(some)MSX Mouse's worked as a "joystick" for playing games.
There were some brands that manufactured the mouses for MSX microcomputers. Microsoft and Yamaha only produced the chips, even if Yamaha also had some MSX specific models.
Some brands that were confirmed to acts as joysticks using a compatible mode were from Philips , Sony and Panasonic. Those brands also had some MSX compatible microcomputers.

Since the graphical user interface was not very popular into Microsoft operating systems, the mouse was primary used for games (shooters) or graphic designer. The 'original' Microsoft MSX-DOS was a glorified CP/M like Operating System ("backward compatible") that used the Sony 3 1/2 floppy disks. It worked well with IBM compatible 5 1/4 and other formats too. There was some reports about it being also capable of use 3 inch or even the old 8 inch disks, but I do not know any disk that BIG! After all the Sony 3 1/2 disks were smaller ...

The Mouse can be used as joystick pressing and holding the left button at the start up or when someone plug the mouse .