Swagger could provide more rich document for your API. ASP.NET MVC also has Web API Helper page, but unlike Swagger, which is more powerful with client generation, discoverablity and more developer support.
This blog will show how to use Swagger to ASP.NET MVC API project and provide list of how to.
With a Swagger-enabled API, you get interactive documentation, client SDK generation and discoverability.
Following are few information relative with Swagger.