Google announced JSON-LD support for Reviews and Products structured data markup.
Webmaster trends analyst John Mueller wrote in a Google+ post (via Search Engine Roundtable) that along with the launch of support for JSON-LD for Reviews and Products structured data markup, they've also "cleaned up" some of their application logic.
"For example, requirements for explicit reviewed item and correct property name values are now enforced. Check your markup in the Structured Data Testing Tool and Search Console Structured Data Dashboard to see if your site is impacted by these changes."
Mueller notes that more info about how to format Reviews and Products markup to comply with Google's validation rules is available here.
"We hope these changes make it easier to use structured data on your side!" he says.
Google released the structured data tool to help webmasters author and publish markup on their sites. It provides validation for all Google features powered by structured data, support for markup in JSON-LD (including dynamic HTML pages).