Postman is pretty handy for viewing the return values of POSTs, but also for debugging during the early phases of development. In my case, I was trying to POST to my Alexa app. developer.amazon.com was reporting a 500 error, but nothing beyond that. This was in the early stages where I had not yet created any sort of logging or error handling in my Alexa API.
Determining the error was best left to localhost where I could debug right in Visual Studio.
Setting things up is a breeze.
Begin by launching the app directly from Visual Studio in a browser.
In Postman, set the type to POST; enter your local URL.
Click on the Params button to the right of the URL. Click the Body tab; change the type in the dropdown to JSON (application/json) or your preferred type. Paste in your payload as raw. Click Send.
Assuming an error has occurred, Visual Studio will respond to the request and display the error inline.