We propose an educational metadata schema for use with mobile learning. The development of metadata schemas has been at the core of the learning technology standardisation process. These proposals have been aimed at conventional eLearning on a desktop computer in a formal training and teaching environment. Our aim has been to specify a metadata schema, based on the existing IEEE Learning Object Metadata and IMS Learner Information Profile standards, to cover mobile and informal learning scenarios. In this paper we describe the design process of the Mobile Learning Metadata (MLM) schema; we explain the new fields and structures introduced or amended with the reasons behind them.