There's not much detail available (that I've been able to find) but the story in a nutshell is here
IIRC, you have to fill in a vast form and be signed off by a GP to receive incapacity benefit. What 'medical assessment' are the Tories going to devise that's going to be more accurate than that? Or are they just looking for a way to take vulnerable people off higher rates of benefits?
Or am I missing something?