This article describes how to customize the tooltip by overriding its default template and the how to display any other value from the items source.
The tooltip in the SfChart can be customized by using the TooltipTemplate property of the DataTemplate. You need to use a converter to get the underlying values from the ChartSegment that comes as DataContext for this data template.
The following screenshot illustrates the output with the tooltip that shows the x and y values of the segments.
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