A key desideratum for many software comprehension tools is to reduce the mental burdens of software engineers. That is, the tools should support cognition. This key benefit is difficult to directly observe and measure, so evaluating such tools has been problematic. This paper describes an investigation into the application of distributed cognition theories to analyzing and observing cognitive support. Theories of cognitive support are used to generate an analysis of potential cognitive benefits provided by the compilation-error tracking facilities of a commercial software development environment. This analysis is used to generate a scheme for coding user observations such that cognitive support related activity can be tracked. Experiences in applying the technique on data from a field study are reported. The study also serves to provide a glimpse into the ways that programmers and tools cooperate. Implications are drawn for future practices of tool evaluation and engineering.