The potential of Computer Games for non-entertainment purposes, such as education, is well established. A wide variety of games have been developed for the educational market, covering subjects such as mathematics and languages. However, while a growing industry developing educational games exist, the practical uptake in schools is not as high as one would expect, based on current evidence of their effectiveness. The EduGameLab project investigates causes and solutions to the relatively low level of uptake in European schools. This paper describes a rating tool for sharing experiences about educational games among educators and parents, developed in the EduGameLab project. The ambition is that sharing knowledge about how games can be used in practice will stimulate practical use and acceptance. The development of this tool is based on a metadata schema for formally describing serious games and experiences with these games.