Programmatically add photos to a shared photo album?

I've got photos coming in from multiple sources on our network that I would like to have automatically redistributed to different shared photo albums in iCloud. I thought this would be a simple Automator app, and it is -- save for the "shared photo album" part. I can ingest photos added to a directory, and put them in an album, but not a shared album; the options for available albums only show the local albums, nothing from iCloud.

I've also checked the AppleScript libraries (including those from photosautomation.com) to no avail. I've also checked the OS X Developers' documentation and found nothing obvious.

Any ideas on how I can do this? Is there a library I'm overlooking, or maybe an application that will do this for me already?

Thanks in advance,

Aaron