This chapter presents an analysis of authentic student texts produced by final-year undergraduate ESP students to examine the pedagogical value of Cognitive Discourse Functions (CDFs). Drawing on three writing tasks completed by students in an EAP elective, we use CDFs to interpret how functions are realised in student texts and how stronger and weaker performances differ in their selection, sequencing, and integration of functions. The three tasks comprise: a diagnostic reflection on disciplinary values (Task 1), a graduation project summary (Task 2), and a problem–solution report aligned with a Situation–Problem–Solution macrostructure (Task 3). Across the three tasks, the texts illustrate: (i) rhetorical flexibility through alternative CDF pathways (e.g., DEFINE-led vs. DESCRIBE-led openings), (ii) disciplinary sensitivity in patterns of CDF salience (e.g., the dominance of DESCRIBE/REPORT in Interactive Technologies project communication), and (iii) points where linguistic resources constrain the successful realisation of intended functions within genre staging. The chapter closes by translating these patterns into concrete teaching implications for task design, modelling, feedback, and the early integration of CDFs into ESP teaching.