Google announced they are sunsetting or discontinuing the original Webmaster Tools API first released back in 2008. The new one was announced in September 2014 and now Google is saying it is time to finally switch over to the new API because the old API is shutting down on April 20, 2015.
The big issue is that the old API supported two things that the new API doest not support including:
- Messages
- Keywords
The big one is the keywords, you can no longer get keyword data for the content report from the Google Webmaster Tools API starting on April 20, 2015. Google did say there are other ways to get the data in Python, Java, and OACurl but many of the free and popular keyword tools use the API. Others just scrape the search results.
In any event, be prepared, if you use the old API, it is shutting down in about a month.
Forum discussion at Google+.