Vision is a plugin that lets you quickly test your GROQ queries right from the Studio. It shows up as a tool in the navigation bar when installed.
To install it, use the terminal and go to the root directory of your Sanity project, and run
sanity install @sanity/vision. If you have the development server running while doing this, you need to restart it in order to see Vision in your Studio.
You can only use Vision to test queries. You cannot use it for mutations.
To learn more about how to write queries for Vision, read How Queries Work - GROQ.
The Vision plugin is an example of a Studio tool. Want to write your own tool? You can bootstrap one by running
sanity init plugin and select it from the list.