You can now test the directives of your robots.txt file and check whether it is working properly. Once you are done with the testing, you can upload the file on the server to bring the changes into effect.
With this tool, you will also be able to review the older versions of your robots.txt file and see the issues that restricts Googlebot from crawling the website.
This is a great new addition in the GWT.
Also See:
Google’s Take on Sitewide Links
List of Meta Tags Supported by Google
Google Human Quality Raters Do Not Influence A Website Ranking Directly
Google Now Cards
List of Meta Tags
Facebook Open Graph Protocol Guide
Rich Snippets in Google
Add Ratings and Reviews on Google Search Results
Seo Guide for Schema
Google Expands Knowledge Graph
Google Disavow Links Tool
Query Highlighting on Google