The action-oriented approach (AoA) is a powerful basis to inform teaching, learning, and assessment in the classroom that identifies learners as social agents and focuses on language learning through language use. This paper answers the call for developments that help teachers teach and learners learn in an AoA-informed way. We argue that cognitive discourse functions (CDFs) align with AoA, helping to develop learner thinking by focusing on the learners' use of language. We complement our conceptual discussion referring to the process of developing a self- and peer-assessment tool informed by AoA and CDFs and the initial application of this tool in an advanced academic writing course in a Japanese university with B1 and B2 level students. We discuss how this tool can guide learners' understanding of their writing process and fosters learners' responsibility for deciding how they mobilize their linguistic resources to express particular language functions.