I was doing some fork maintenance the other and noticed a strange clip that is mounted on one of the screws used to attach the caliper to fork. The pictures below show the clip in question. It really looks like the clip is designed to attach on the screw (the screw has dents, and the clip has the matching ones) ...but: I only saw it one of the screws, and only on the front brake. I didn't see any on the rear brake, nor on another bike at home that uses the same calipers and fork (unless they've been lost).
this manual (https://www.manualslib.com/manual/1590153/Shimano-Br-M8000.html?page=12#manual) suggests the clip is supposed to keep the bolt from coming off.
I'm not sure it is really capable to do that. But it would help noticing if the bolt became loose, because it would change position when it does.