We address in this article the description and usage of component protocols viewed as specific services. In addition to inter-component service composition, our \kmelia component model supports vertical structuring mechanisms that allow service composition inside a component. The structuring mechanisms (namely state annotation and transition annotation) are then used to describe protocols which are considered here as component usage guides. These structuring mechanisms are integrated in the support language of our component model and are implemented in our COSTO toolbox. We show how protocol analysis is performed in order to detect some inconsistencies that may be introduced by the component designers.