Typing "/kill @e[type=!Player,r=1,c=1]" when there are no nearby entities besides yourself (All entities are outside of 1 radius of you) produces the error "The entity UUID provided is in an invalid format" despite the fact that the format is actually correct and it just can't find an entity to kill. This is not an issue if you remove the radius, count or type arguments (Removing type just kills you). This works for all types and radii that I tested, but only if count is 1.

Code analysis by marcono1234 can be found in this comment.