VQSR training set

Hi all,
I would like to try applying VQSR to my WGS data. What I could use is a SNP database built with GBS on different samples than the ones present in my actual callset. I have a question: do we need variant annotations in the training set, or is it useless (can't figure it out)? If we need it, what type of annotations are mandatory? Should they be strictly the same as the ones present in my actual callset? What happens if it is not the case?
Thanks!
Ben