The growing demand for integration among different applications, devices and platforms has increased the need for Web-based interfaces to connect them. While “Web services” (or SOA) were relatively recently used to provide this connectivity, today “Web APIs,” “APIs” or “API programs” are being used. Because APIs emphasize a developer-centric view of integration, there is a focus on usability. Usability is important because of the two main API business drivers: growth in the API usage and the reduction of application development costs. If examining how developers learn, use and get feedback from Web APIs, key interactions can be categorized in four ways: discovery, learning, invocation and analysis.