AppleScript mouse position

Short answer is, you probably can't. There used to be some osaxen that would do it (all the way back in os 9), but applescript isn't really well-suited for capturing events of that nature and I don't know of any way to do it in os X.

What's your bigger goal in this? there might be a different way to approach what you're trying to do.

for what purpose, and in what context?

Take a look at MouseTools.

On 10.9 and later you can now do this:

use framework "Foundation"

use scripting additions

set theList to current application'sNSEvent'smouseLocation()

(*

set xCoord to theList's x

set yCoord to theList's y

*)