I syndicate to Mastodon in a few ways/methods. I’m using Pfefferle’s Activity Streams plugin to make my entire site appear like a Mastodon instance @firstname.lastname@example.org, but that’s a work in progress, though it does pull responses back.
Otherwise, I’m either using functionality built into the Syndication Links plugin or Mastodon Autopost plugins for WordPress to syndicate and then getting backfeed via Brid.gy.
All these plugins are in the WordPress repository and/or Github if you want to look at their code.
In short, it’s not a complete problem I’ve “solved for” yet, and I’m still experimenting and watching several projects to see what works best in the end.