positioning and rotating pivoting tool, on robot arm

Hi.
I am new to final IK. so hoping someone can just point me in the right direction (which final IK tools you would use).
I am rigging a robot which has 2 main control buttons which are used to position a tool on a robotic arm.
The bottom button is moved to position the tip of the tool (that defines the tools pivot point xyz position) : The top button is moved to rotate the tool around that pivot point, without changing its position: I have used hinge joints for the main part of the arm, and that all works OK.

But not sure how set up the rig to make the arm (tool/hand) rotate around the lower point. Final IK has so many tools, I would love to hear some advice on which tools you would use to rig this movement, and what shape you would make the IK skeleton.