API to send email to an existing contact in the list?

Hi,
Our users opt-in to receive specific offers on our Website - we'd like to use an API to send an email (a pre-set template in ConstantContact) with the offer.  These users may be new contacts or existing contacts.
1) Existing contacts - What's the API to send an email to an existing contact?  This is a very common use-case, yet i don't see an option in the REST API spec
2) New contacts - i guess i can set up an auto-responder  email template and use the API to add a contact.  The autoresponder will email the offer to the new contact, correct?
3) Are there parameters/variables i can pass thru the API to the email template e.g. "image link", "offer description", etc. - didn't see this in the REST API doc - http://developer.constantcontact.com/doc
thanks
Kiran

Hi Kiran,   The API can be

Hi Kiran,
 
The API can be used to add contacts which can trigger a welcome email or auto-responder, but there is no current solution for sending an email through the API. All of the API calls are listed here: http://developer.constantcontact.com/doc/reference.

Dan H
Support Engineer, Constant Contact