mpdupdate is a very simple plugin for beets that lets you automatically
update MPD's index whenever you change your beets library.
To use it, enable it in your config.yaml by putting mpdupdate on your
plugins line. Then, you'll probably want to configure the specifics of your
MPD server. You can do that using an mpdupdate: section in your
config.yaml, which looks like this:
mpdupdate:
host: localhost
port: 6600
password: seekrit
With that all in place, you'll see beets send the "update" command to your MPD server every time you change your beets library.