Measure and Field Descriptions Visible to Users on Service

Descriptions are currently set in the Properties pane in desktop, and are then only visible to other desktop users. At our scale many of our users are only using the online service and creating multiple fields/measures for descriptions to then set as tooltips is not feasible. Descriptions would ideally allow for visibility on the service that could be toggled on/off through the Specific Column settings on a selected visual. The default setting would be 'off' but when toggled on, the description would show as a hover-over tooltip at the column header.