Hello Chris,
Yes, it is possible to use a RadToolTip for displaying a ValidationSummary. In order to achieve this you must go through the following steps:
1. Add a ValidationSummary object to your RadToolTip.
2. Write a javascript function to check the validity (the easiest way to do this is by checking the display of the ValidationSummary object - if it is "none", there are not invalid values) and cancel the RadToolTip pop-up if everything is correct.
3. Initialize the "OnClientBeforeShow" property of the ToolTip with this function.
A demonstration of this approach can be found
here.
Greetings,
Svetlina
the Telerik team