To meet the current trends in higher education, there is accountability on EAP programmes to prepare and assess students’ access to higher education. Thus, multimodal tasks including integrated writing (IW) assessments have seen a resurgence because they arguably closely mirror academic writing. However, test practicality constraints and variability in the use and format of these assessments mean rating scales often fall short in substantiating the central claims of IW assessment. We developed an integrated reading-writing scale taking into account reading-writing requirements and empirical research on IW tests designed to assess readiness for first-year humanities and social science courses. We approached test development as part of the ongoing validation efforts, detailing the considerations involved in the scale development process. We argue that alignment with academic writing requirements should guide the development of IW tests, thereby acknowledging and comprehending nuances of academic writing. The paper demonstrates considerations and decisions in scale design as the validation process from the start, which is a reminder that assessment is not just a quantitative exercise but a multifaceted process. • The design of a rating scale for first-year undergraduate academic writing is detailed. • Emphasis is placed on the role of reading in integrated writing scales. • Academic argumentation, rather than solely source-use mechanics, is considered. • Implications for construct operationalisation in academic evaluations are offered.