Простой и наглядный пример интеграции Swagger в ASP.NET Core приложение
https://docs.microsoft.com/en-us/aspnet/core/tutorials/web-api-help-pages-using-swagger
https://docs.microsoft.com/en-us/aspnet/core/tutorials/web-api-help-pages-using-swagger
Docs
ASP.NET Core web API documentation with Swagger / OpenAPI
This tutorial provides a walkthrough of adding Swagger to generate documentation and help pages for a web API app.