The DevTools AddOn is a small addon which provides tools for developers of UI mods, particularly for examining the World of Warcraft API. It's primarily a tool I built for myself but I figured I'd share it in case it's useful to others.
Example from /dump ChatFrame1
/dtchatevent links and tooltip
/dtframestack info tooltip
Just a shortcut (since I'm lazy) for /script ReloadUI()
/dump expression Edit
Prints the result of executing a LUA expression (Basically /script but with output). It should be able to handle pretty much any kind of return data (including self-referential nested tables!)
/dump GetPlayerMapPosition("player") DevTools: value=GetPlayerMapPosition("player") 0.43320921063423 0.69365233182907
Toggle chat event tracking/debugging (this is a saved setting). When active each chat frame message (in all standard ChatFrames) will be prefixed by a marker that can be clicked on the pop up the details of the event that created it.
Displays the current chat event rolling buffer size.
/dtchatevent buffer <size>
Set the current chat event rolling buffer size (e.g. /dtchatevent buffer 10000), the default buffer size is 1000.
Toggles the 'frame stack' window, which displays the stack of visible frames under the mouse pointer. (There are also key bindings for this).