Azure API Management, while a popular choice, is not open-source. API management tools help developers design, version, document, secure, and monetize their internal or external APIs. An API gateway acts as a proxy for API resources, controlling, facilitating, and managing incoming traffic. API management systems comprise different components that facilitate various processes. The best API management tool depends on individual needs and can be determined by evaluating top tools such as RapidAPI, Apigee, Mulesoft, Postman, Tyk, WSO2, and Gravitee.io. Each tool offers unique features, pricing models, and integration capabilities, making it essential to research and compare them before making a decision.