Update: Clarified AdGroupType values introduced in v201705.
Update 06/22/2017: Clarified information in last paragraph.
Starting this week, users of the new AdWords interface will be able to create 
dynamic search ads (DSA) through the new 
dynamic ad group type in Search campaigns with Dynamic Search Ad settings. This has some consequences in the AdWords API as described below.
How does this impact the AdWords API?
If your managed accounts are eligible for the new AdWords interface, be aware that if users create dynamic ad groups in the interface, 
AdGroupType values for the dynamic ad groups will be returned as 
SEARCH_DYNAMIC_ADS in v201705 and 
UNKNOWN for earlier API versions. Here are the rules applied to the dynamic ad group type:
As described in 
this guide, to create dynamic search ads in the AdWords API, some settings and criteria are required, such as 
WebPage and 
DynamicSearchAdsSetting. These settings can still be added and modified in the dynamic ad group type.
What should you do?
If your application manages accounts that have access to the new AdWords interface, or if you have ad groups with type 
SEARCH_DYNAMIC_ADS for v201705 and 
UNKNOWN for earlier versions, ensure that you properly handle these cases by:
In addition, for v201705, you 
cannot add features related to Dynamic Search Ads to ad groups with 
AdGroupType of 
SEARCH_STANDARD. Examples of Dynamic Search Ad features include the 
Webpage criterion and 
ExpandedDynamicSearchAds. However, for the earlier versions, ad groups with 
AdGroupType of 
SEARCH_STANDARD are 
not affected by this change. You can still continue adding expanded text ads, dynamic search ads, call ads, and 
various criterion types to them.
As always, if you have any questions, please post on the 
forum.
 - Thanet Praneenararat, AdWords API Team
 - Thanet Praneenararat, AdWords API Team