What are some alternatives?
Postman - Postman is the most efficient way to test, develop and document APIs.
Apigee - Intelligent and complete API platform
Tyk - Tyk is an open-source API gateway and API management platform.
WSO2 API Manager - WSO2 API Manager is a 100% open source enterprise-class solution that supports API publishing, lifecycle management, application development, access control, rate limiting and analytics in one cleanly integrated system.
Paw - Paw is a REST client for Mac.
MuleSoft Anypoint Platform - Anypoint Platform is a unified, highly productive, hybrid integration platform that creates an application network of apps, data and devices with API-led connectivity.