Mobiledeviceinvitations API - Proper XML form

I am looking for the required fields for the proper creation of a mobile device invitation.

<mobile_device_invitation>
  <sent_to>drew.peterson@domain.com</sent_to>
  <sent_from>JSS</sent_from>
  <reply_to>helpdesk@domain.com</reply_to>
  <subject>Mobile Device Enrollment Invitation</subject>
  <message>Tap the link to enroll your mobile device.

    %@
</message>
  <username/>
  <invitation_type>EMAIL</invitation_type>
  <error_message/>
  <login_required>false</login_required>
  <multiple_uses_allowed>true</multiple_uses_allowed>
  <expiration_date>2016-06-17 13:26:00</expiration_date>
  <expiration_date_utc>2016-06-17T13:26:00.000+0000</expiration_date_utc>
  <expiration_date_epoch>1466169960000</expiration_date_epoch>
  <enroll_into_site>
    <id>-1</id>
    <name>None</name>
  </enroll_into_site>
  <keep_existing_site_membership since="9.4">false</keep_existing_site_membership>
  <site>
    <id>-1</id>
    <name>None</name>
  </site>
  <target_ios>iOS 4</target_ios>
</mobile_device_invitation>

Is what I have so far, and it gives me a result of Enrollment Incomplete.