See the question and my original answer on StackOverflow

The property grid is "open source".

This description text is set by this,4496


And gridEntry for a category is handled by the CategoryGridEntry class which derives from GridEntry class which defines PropertyDescription property here,909 by this:

  public virtual string PropertyDescription {
            get {
                return null;

This property is not overridden in CategoryGridEntry, and all this is internal code, so, no, you can't have a description for categories grid entries.