https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.1.md#operationObject
https://editor.swagger.io//?_ga=2.189566187.1340829731.1521285660-211899350.1521285660#/
https://github.com/domaindrivendev/Swashbuckle
https://docs.microsoft.com/en-us/aspnet/core/tutorials/web-api-help-pages-using-swagger
Alternatives:
http://dapperdox.io/
https://readme.io/
https://github.com/jensoleg/swagger-org
http://stoplight.io/
https://raml.org/
https://apiblueprint.org/
https://apiary.io/
