What is get_tcp_force ? force at the tool flange or TCP?

Hello, dear community.

I am developing a screwing tool and I using an external tool and the UR5e. I am a little confused about the get_tcp_force function.
This is my mockup
image

Does get_tcp_force return the external force/torque read from the sensor mounted in the robot tool flange?
or
Does get_tcp_force return the forces/torques reader from the force sensor in the tool flange and transform its values to the TCP that has been configured?