If i have Tool with Arguments: $(FilePath) and i try to use it when there is no documents open,
that tool doesn't open without document.
Test that for example with Notepad.exe
Ahhh, I see the problem ...
In Tools->customize->Tools adding a new tool fails if you don't use an explicit path because when poide is running the path is set only for pelles tools.
Similarly if you use an explicit path, but use $(filepath) in the command line arguments, the tool won't open if the IDE has no documents open at the time.
I agree, that's a bit of a problem... with no documents open $(filepath) should be a 0 length string.