Tooltips are added since Telerik Reporting R1 2017. The feature allows you add custom text and title of a box displayed on hover of an elemnt in a Telerik Report. All report viewers provide support for displaying tooltips in a report viewer’s native rendering technology. Tooltips are supported also in PDF files.
Each Report section and item has a Tooltip property where you can configure the Text you want to appear on hover. You can also specify a Title for the tooltip's box.
The Series collection of the Graph item also has support for tooltips.
HTML5 Viewer: viewerToolTipOpening(e, args)
WPF ReportViewer control: ViewerToolTipOpening event.
WinForms ReportViewer control: ViewerToolTipOpening event.
If you use the HTML5 Viewer, the new Tooltips functionality requires additional Kendo UI dependency. This dependency is included in the Kendo UI subset bundle provided by Telerik Reporting - telerikReportViewer.kendo-220.127.116.117.min.js.
If you use a custom set of Kendo UI widgets, you can load kendo.tooltip.min.js of your version (2015.3.1111+) of Kendo UI.