Adapting heterogeneous software components that present mismatching interaction behaviour is one of the crucial problems in Component-Based Software Engineering. The process of component adaptation can be synthesized by a transformation from an initial specification (of the requested adaptation) to a revised specification (expressing the actual adaptation that will be featured by the deployed adaptor component). An important capability in this context is hence to be able to evaluate to which extent an adaptor proposal satisfies the initially requested adaptation. The aim of this paper is precisely to develop different metrics that can be employed to this end. Such metrics can be fruitfully employed both to assess the acceptability of an adaptation proposal, and to compare different adaptation solutions proposed by different servers.