Call-only ads in AdWords allow you to show mobile-ready ads that feature a click-to-call button and descriptive text, so your customers can call you directly from mobile search results. The AdWords API v201409 release introduced support for call-only ads through a new creative type: CallOnlyAd.

These new CallOnlyAds are set up just the same way as TextAds, with the addition of a few fields useful for the new type. In Ruby, for example, you would set up a new CallOnlyAd with a hash like this:
  :xsi_type => 'CallOnlyAd',
  :description1 => 'Visit the Red Planet in style.',
  :description2 => 'Low-gravity fun for everyone!',
  :display_url => '',
  :phone_number => '(555) 555-5555',
  :business_name => 'Universal Cruises',
  :call_tracked => true,
  :phone_number_verification_url => ''
You can also set the conversionTypeId if you want to measure calls in a specific conversion type. Otherwise, tracked calls will use a default conversion type.

The phoneNumberVerificationUrl is a new field for CallOnlyAds. If included, we will crawl the page you specify to look for the phone number for verification; this can speed up the approval process. Otherwise, we will have to crawl your entire website.

Previously, call-only ads were set up using feeds, specifically with the ONLY field (placeholder ID 4) within the Call placeholder type (placeholder type ID 2). The ONLY field will sunset in June 2015, so you should finish migrating all your existing call-only ads to the new CallOnlyAd creative type before that time. It is recommended that you create new campaigns to house your CallOnlyAds separately from other ad types.

As always, if you have any questions about this change, please contact us on the forum or via our Google+ page.