Most current mobile agent systems are based on programming languages whose semantics are difficult to prove correct as they lack an adequate underlying formal theory. In recent years, the development of the theory of concurrent systems, namely of process calculi, has allowed for the first time the modeling of mobile agent systems.Languages directly based on process calculi are, however, very low-level and it is desirable to provide the programmer with higher level abstractions, while keeping the semantics of the base calculus. In this technical report we present the syntax and the semantics of a scripting language for programming mobile agents called Mob. We describe the language's syntax and semantics. Mob is service-oriented, meaning that agents act both as servers and as clients of services and that this coupling is done dynamically at run-time. The language is implemented on top of a process calculus which allows us to prove that the framework is sound by encoding its semantics into the underlying calculus. This provides a form of language security not available to other mobile agent languages developed using a more ah-doc approach.