Functionality
The Toolbox is composed of commonly used functions, but not the most commonly used functions. As a result, it grew into a hodgepodge of different API libraries. The Toolbox encompasses most of the basic functionality which distinguished the Classic Mac OS. Apple's references “Inside Macintosh: Macintosh Toolbox Essentials” and “Inside Macintosh: More Macintosh Toolbox”, similarly vague in scope, also document most of the Toolbox.
Read more about this topic: Macintosh Toolbox