Dear editor,rnApplication programming interface(API)documentation plays an important role in software development and reuse[1]for both API maintainers and API users.Well-written documentation helps developers understand and reuse codes effectively[2]and focus their time on desired in-terfaces and functions instead of the entire system[3].Most high-quality open source projects maintain complete and in-formative official documentation.API documentation typi-cally conveys detailed specifications,such as class/interface hierarchies and method descriptions,which can be of great benefit to developers[4].However,despite its authoritative-ness and thoroughness,single-sourced official documenta-tion does not always meet the developers'requirements[5].As of January 2018,over 1 million posts about Android had been posted to StackOverflow and approximately 16％of these posts were related to its API(statistics found by searching for API and Android in StackOverflow).The lack of important information in API documentation makes de-velopers spend large amounts of time searching for informa-tion and seeking help.During this time,developers obtain large amounts of unconfirmed information,which can affect the quality of projects and the developers'understanding of the API.