May be it is already available and thus not really todo (feel welcome to close then or I will), and/or I have asked before, but I failed to find it. Sorry if duplicating the issue.

In some scenarios we do know ahead of time url + size + filename (thus extension) + corresponding checksum for the content. We would like to implement addurl which would not even talk to the remote server but just "mint" corresponding path to the key under .git/annex/objects and registerurl to it. But I failed to find a convenience annex command which would allow us to get the full key (accounting for E the way git annex does), and full path to it (thus adding DIRHASH which special remotes could "query", and which is appropriate given the repository settings).

I made subject prefixed with calckey since it seems like the closest hit but it does need an actual file.

edit1: I was pointed to forum/Is_it_possible_adding_files_to_git_annex_bypassing40some_parts_of41the_git_annex_tools/#comment-a80b2371012dda93ad7fb4926af91b48 which seems to be the closest hit, but relies on assuming how extension is extracted by annex, which might be incorrect for some files.

done --Joey