Reassessed to WRAG - not sure what to do next

OK, so I've had a letter from the DWP saying they are changing to amount I will be paid because I've been reassessed into the WRAG group. Is that the only notification I get about the outcome of my assessment, or are they meant to send me a letter outlining the reasons for their decision as well? I'm in two minds as to whether I should put in for a mandatory reconsideration, due to the risk of them deciding that I'm actually fit for work after all,but on the other hand there's the risk that I'm not able to comply with what my work coach (no idea who that is) expects me to do, and I end up getting sanctioned. Fortunately, I've been claiming ESA long enough that the drop in payments is significant, but not as horrendous as dropping back to JSA levels, but I think it also means I'm eligible for less council tax support too.

So, it seems I haven't scored enough points on the descriptors to be put into the WRAG, but they've assigned me to it based on Reg 29. If I were to request an MR on the basis that Reg 35 applies as well, do I need to detail the areas where I think I should have scored points but didn't too?