Developing modern mobile applications often require the uses of many libraries specific for the mobile platform, which can be overwhelmingly too many for application developers to find what are needed for a functionality and where and how to use them properly. This paper presents a tool, named LibraryGuru, to recommend suitable Android APIs for given functionality descriptions. It not only recommends functional APIs that can be invoked for implementing the functionality, but also recommends event callback APIs that are inherent in the Android framework and need to be overridden in the application. LibraryGuru internally builds correlation databases among various functionality descriptions and Android APIs. These correlations are extracted from Android development tutorials and SDK documents with domain-specific code parsing and natural language processing techniques adapted for functional APIs and event callback APIs separately, and are matched against functionality queries to recommend relevant APIs for developers. LibraryGuru is publicly accessible at http://libraryguru.info, and a demo video is available at https://youtu.be/f7MtjliUM-4.