Application programming interfaces (APIs) have a central role in software development, as programmers have to deal with a number of routines and services that range from operating system libraries to large application frameworks. In order to effectively use APIs, programmers should have good comprehension of these software artifacts, making sense of the underlying abstractions and concepts by developing an interpretation that is compatible with the designer s intent. Due to the complexity of today s systems and programming environments, learning and using an API properly can be non-trivial task to many programmers. Traditionally, studies on API design have been developed from a usability standpoint. These studies have provided evidence that bad APIs may a effect programmer s productivity and software quality, offering valuable insights to improve the design of new and existing APIs. This thesis proposes a novel approach to investigate and discuss API design, based on a communication perspective under the theoretical guidance of Semiotic Engineering. From this perspective, an API can be viewed as a communication process that takes place between designer and programmer, in which the former encodes a message to the latter about how to communicate back with the system and use the artifact s features, according to its design vision. This approach provides an account of API design space that highlights the pragmatic and cognitive aspects of human communication mediated by this type of software artifact. By means of the collection and qualitative analysis of empirical data from bug repositories and other sources, this research work contributes to a deeper comprehension of the subject, providing an epistemic framework that intends to support the analysis, discussion and evaluation of API design.