netmeg - 1:47 am on May 1, 2013 (gmt 0)
Write it yourself for a COUPLE of pages, and see if you notice an improvement.
But honestly, 100 words, or even 300 words per page is not going to make that much difference in my opinion, specially if they're just written to make Google happy.
(That's a pretty boilerplate recommendation from your SEO company; I hope you picked a good one)
Your site needs to project the signals that will make users consider it to be synonymous with whatever your niche is. Trust, authority, and why your users love you and how you're better than everyone else. Adding text to category pages may not be sufficient to help with that.