Merge title short description

I’m setting up an auto-email with Mailchimp to send out my blog posts. I have a merge tag that displays the link title of my most recent post; however, underneath the title, I’d like to include a brief one-or-two-sentence description of the post. E.g.,

(Title) “WordPress forums are great.”
(Description) A post about how great WordPress forms are.

What merge tag can I use to automatically place a short description underneath the title? Where would I write this description in my WordPress post so that the merge tag could automatically add it in?