Abstract-Web APIs, characterized by their relative simplicity and their natural suitability for the Web, have become increasingly dominant in the world of services on the Web. Despite their popularity, Web APIs are so heterogeneous in terms of the underlying principles adopted and the means used for publishing them that discovering, understanding and notably invoking Web APIs is nowadays more an art than a science. In this paper, we present our work towards supporting the automated invocation of Web APIs. In particular, we describe a framework that provides a unique entry point for the invocation of most Web APIs that can be found on the Web, by exploiting non-intrusive semantic annotations of HTML pages describing Web APIs in order to capture both their semantics as well as information necessary to carry out their invocation.