The tooltip only takes a string for its value. How the string is created is the developer's decision and task. You can query your database wit your code and return a value to pass to the tooltip.
In case you want to have the tooltip load content based on both keys - you can concatenate the strings with a special character inbetween (e.g. a | symbol) and in the OnAjaxUpdate event the tooltip manager offers you can split the Value that is passed, get your keys and query your database again. See this demo
for another example of this logic.
the Telerik team
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