Nowaday, pratically every application should one day or the other add drag and drop features.
The principle is very simple: you paste, paste selection or drop things into the window and a list of all MIME types the source application can export is shown, with the data of each types, so you can view what data organization is to code filters for your program.
I initialy created this tool to be able to make BasKet (http://kde-apps.org/content/show.php?content=10020) understand the most MIME types every application can drag to it: I need to analyze what are the provided MIME types and what they contain. And this tool allow to boost up the work. Another developer previously asked me if I was using a special program, so I know it will be usefull to at least another person than me :-D
12 years ago
Close to final one: it's a very simple (but usefull) tool.