How to get all options for a given field or set of fields

I’ve got a multi select field on my issues and I’m not able to find an API that will return all of the possible options. Right now I just want to make sure I’ve got the labels cached in my system and I’m unable to find an API that will return all possibleValues for just a set of fields.
I did find that the GET /search API will return the details if I include expand=editmeta but that means I have to process possible values for every single issue that comes through my system. I’d prefer a more efficient way to just get the metadata about the field instead of “hacking” it through the GET /search API.
Does any API actually return this data?
This field does not have any context (or at least a 404 is returned from GET /field/mycustomfield/context) so going that route has also not worked