In what has been a (very) long time coming, Google just announced a feature that allows site owners to grant “limited” access to a site’s data and setting in Webmaster Tools.
The platform previously offered site owners the ability to grant full verified access to a Webmaster Tools account, but that presented some security risks in that anyone added as an owner could add anyone else they wanted as an owner which presents some obvious control issues. With this new administration feature, however, setting specific permission levels is now a reality. Instead of adding or removing owners, you’ll be adding or removing “users”.
Webmaster Tools site “owners” will be able to add or delete up to 100 users and specify each user's access as full or restricted. Those users who are added through the user administration page are tied to a specific site. Should for any reason you become unverified for a particular site, any users added will lose their access.
Users with full permission will be able to view all of the data and take most of the actions (changing site setting or demoting sitelinks) with Webmaster Tools, whereas Restricted users will have access to view data and take some actions including using some of the account features like Fetch as Googlebot and message configuration. Google has put together a list of the features and actions that are accessible as a full or restricted user.
Below is a screenshot of the user administration page used to assigned permission levels in Google Webmaster Tools.