AppStream is a metadata specification which permits software components to provide information about themselves to automated systems and end-users before the software is actually installed. The AppStream project provides facilities to easily access and transform this metadata, as well as a few additional services for building feature-rich software centers and similar applications that make use of software metadata.

The appstreamcli command-line tool allows to read, write, and transform AppStream XML or YAML metadata as well as to validate it for compliance with the specification. It also provides easy access to the system metadata pool, for example to query for software that provides a specific Mediatype handler or for installing software by its component identifier.