Postman - The Collaboration Platform for API Development
Freshservice - Freshservice: the one-stop cloud solution for all your IT management needs.
Django REST framework - Django REST framework is a toolkit for building web APIs.
Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community
Tibco Mashery - API management
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.