You could change the Tool diameter in the Cam program and repost it, so if you tool is 6mm change it to 6.5mm in the software repost the program and recut the part, you use the same tool in the machine, but the program thinks it is bigger and will cut .5mm larger each side, so this is simple to do, this is for outside a part if it is inside the and you want the pocket bigger post the cutter as smaller to make the pocket larger
You could also use cutter comp G40 G41 G42 in your program and then change this Tool offset in the control. either way you still have to redo your program to use cutter comp