Does migrate_d2d create custom fields?

Hi,

I've read this very interesting article about the drupal-to-drupal data migration: http://www.acquia.com/blog/drupal-drupal-data-migration-part-1-basics

However, I'm not yet sure whether I've understood a quite basic aspect yet: Is the migrate_d2d-module able to create a custom field in the destination database on its own, or does this custom field has to be manually created before a migration process can be started, which then maps a custom field from a legacy database to the destination database?

I'm currently developing a custom migration module to migrate my (heavily customized) d6 site to d7. I'm stuck with the user migration so far. There are 27 custom user fields (like 'first_name' and so on) in my d6 database, which I have to migrate to an absolutely fresh d7 database.

So far I've used $this->addUnmigratedSources to exclude them from being mapped to any destination field (just for test reasons). Will I have to manually create all these custom user fields or is there a way to do this programmatically with migrate_d2d?

Best regards,
Miro