According to best practices, data-related code that accesses data from the database or otherwise would benefit multiple forms should be placed on the table. Examples of this are display methods, validations and business logic to be executed on inserts, updates, deletes.
It would be logical to think tool tips would be included as well, and there is a record method called toolTipField() which can be overridden in your table.
Only problem is, it’s not working. (At least not in 2012R3) The code doesn’t even get called.
To work around it, add the tool tip code directly to your forms instead. Not best practice according to the book, but what works will always trump what doesn’t…