foxtools.fll contains several useful functions. In VFP 3.0 it was the only way to access functions in DLLs. This can now be done using DECLARE DLL. Most of the foxtools functions are now part of the language in VFP 6.0, so it's mainly of use in 3.0 and 5.0.
There's a help file in the files area here. Look in the Coding, syntax & commands section for a file titled Extended Foxtools Help. It's written by George Tasker and includes descriptions of all the foxtools functions.
>what is use of foxtool.fll