Looking at https://friend.camp/@bookmarks@dfk-postmarks.glitch.me it seems that posting links with hashtags would give you the same functionality.
That said, I'm not sure it's json-ld compatible. Seems to assume the common format, not the infinite other semantically-equivalent ways of structuring data. Though I really don't know if that's normal for mastodon-targeting stuff or if I'm missing a higher level request transformer that frames it into what they seem to assume.
As it stands though: pleasantly readable code! I got curious and explored around a bit and it's all remarkably simple. Maybe it needs more error handling or auth or something and it'll grow before it's "ready", but it's nice to see something simple occasionally. You can probably keep a lot of those simple-structure assumptions if you frame your incoming requests to look like the common structure you're using now, if you can find a library that handles that for you: https://www.w3.org/TR/json-ld11-framing/ (which is a lot of text to say "it's a templating system")