In order to build websites, apps or API's, every developer ultimately ends up curating a suite of tools that can help them build products better, cheaper and faster. Below are a few tools that I use all the time.
Postman - Google Chrome plug-in that helps you craft CRUD requests
PAW for Mac - Paw is like Postman
but for Mac users who prefer nice design. I love PAW.
RedBot - Redbot helps you figure out what your headers are returning.
Mashape - Mashable is a marketplace for API-only services. If you ever want to make money from the service your API offers, this is it.
Amazon Lambda - Amazon Lambda is a game changer. You can write a single method, host it on Lambda and let Amazon manage everything else. No need for servers, no need to worry about scaling, it's a big deal.