A tool in MotionBuilder is a new user interface layout adding to the current functionality of the software. Extensive user interface elements are available.

The FBTool class (found in the fbtool.h file) is manipulated as a layout, with all of the functionality that comes with a traditional layout. Regions can be added, moved, and controlled.

The FBTool class is the most versatile of all of the plug-ins, as it imposes no constraints on you, essentially opening up the interface to be added to in any way desired.