There are a million metadata checking sites, but there's only one you really need to be concerned with:
https://search.google.com/structured-data/testing-tool
That won't tell you if anything is
missing, because theoretically only a few very basic meta tags are required on a web page. Once you get past those, there are an endless variety of opinions on how to implement metadata.
Which means you can't really check for what your friend believes is missing, you have to ask them. Or you could just trust that the Xenforo lads will get it right. Either way.