What are some alternatives?
Postman - Postman is the most efficient way to test, develop and document APIs.
MuleSoft - MuleSoft provides an integration platform for connecting any application, data source or API, whether in the cloud or on-premises.
Gravitee.io - Gravitee.io is a flexible, lightweight and an open source API management solution.
Apiary - Collaborative design, instant API mock, generated documentation, integrated code samples, debugging and automated testing
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.
Kong - An open-source management layer for APIs and microservices.