Info mouse-over for Custom Fields to define what it's for

Request: I'd love to see an i with a circle around it on custom fields where when I float my mouse over the i for more information I see a definition of what that field is for and guidance on how to use it.  This could be from the Task Pane next to the clock icon that appears (for the history of data entered into that field) or at the top of columns on table view.  It would allow me to provide more information to users how how to fill out that field to support accurate use feeding reporting.

Example Use Case:  We want to prioritize all incoming requests based on several attributes / custom fields.  If I want my team to provide a 1-5 ranking on Urgency (a custom field) I want that mouse-over to include additional information on how we define Urgency (i.e. Defects, Delivery Date within 60 days, Leadership Request, etc.).  (on this example, I can't use a drop-down box of Urgency types because we need a 1-5 ranking for mathematical calculations of prioritization on an Analyze Board)