This is a Visual Studio plugin for the ADO.NET Entity Designer. It hooks into the model update process in order to pull MS_Description extended properties from a SQL Server database and populate an entity model's (.edmx file) Documentation nodes with them. This makes these descriptions available for use during code generation, enabling the addition of comments to generated classes and members.
The plugin searches the project that an .edmx file belongs to for an App.config containing an Entity Framework connection string so that it can connect to the database.
You can download the extension from the Visual Studio Marketplace.