I'm using the All In One SEO Pack Pro plugin for WordPress.
I've asked their tech folks if I could use MarsEdit to write my posts and still have it processed through their software. They said 'yes' and showed me how to expose some hidden custom fields to MarsEdit:
_aioseop_title - The title
_aioseop_description - The description
_aioseop_keywords - The keywords
title, description and keywords should have corresponding variables with Labels in MarsEdit.
Using the Custom Fields utility (MarsEdit Label :: Server Custom Field Name), how do I set this up? Where is the documentation for the labels of the MarsEdit fields?