But, if comments really are needed, another easy way to have comments is have a file that rides to the side of any json files or docs. Sometimes we use a markdown/text file next file.json -> file.json.md / file.json.txt to describe overall or a file.meta.json that has comments per key. This is only needed sometimes for physical files. If json is from the server, commenting can be done there or in docs if needed.
Well, I sometimes use both C-style (/* ... */) and C++-style (// ...) comments in the same file to sort of mark the relative importance of comments. But yeah, I guess that's not strictly necessary, I could do without.