+1
API should allow file upload/download
The API does not appear to allow attached files to be uploaded or downloaded; nor can you access or update custom fields. This is a big problem when it comes to storing things like Certificate files when you want to have them automatically downloaded and installed by configuration management software.
Customer support service by UserEcho
The GET /read/item or /find/item API calls should return an optional additional field per item, "attachments", with an array of hashes holding file IDs and names (and maybe sizes too).
Then a separate call, GET /read/attachment/<itemid>/<fileid> could return the attached file, with the correct MIME type etc.
For writing attachments, use POST /add/attachment/<item>/<name> and include the MIME type and encoded file as the post body.
For deleting, just GET /delete/attachment/<itemid>/<fileid>
It appears this has now been done (at least, its in the documentation). However there is no way to *delete* an attachment via the API, so if you want to update one (eg, remove the old private key and add a new one) then it seems it is not possible?