In the middle of this year, Google released the Structured Data Dashboard for Google Webmaster Tools. Now, Google announced a useful upgrade to show errors in the tool.
The new feature will now help you understand your markup implementation and debug the issues easily. How so? Through displaying the items with errors in the report and letting webmasters drill deeper into those errors.
The next report shows the errors over time:
Followed by a way to drill into the details:
This may help a ton of webmasters with structured data issues.
Forum discussion at Google+.