We propose to represent the "basic behaviors" of MPEG-7 description tools as a set of constructor, operator and function signatures. This way of making explicit the behavior of datatypes using function signatures is commonly used to formalize data models.A major advantage of this proposal is that, based on signatures, functions can be implemented using different algorithms and technologies, which could be considered as an MPEG-7 API. It?s important to note that the specification of signatures and their description is application independent. It therefore respects one of the major features of MPEG-7, which is "application independency". Implementations of the functions? cores are clearly out of the scope of the standard. Inevitably, the use of an MPEG-7 API makes building MPEG-7 applications easier and more effective as developers would not be totally dependent on the understanding of the MPEG-7 semantics and examples part.