The Writing Mentor TM (WM) application is a Google Docs add-on designed to help students improve their writing in a principled manner and to promote their writing success in postsecondary settings. WM provides automated writing evaluation (AWE) feedback using natural language processing (NLP) methods and linguistic resources. AWE features in WM have been informed by research about postsecondary student writers often classified as developmental (Burstein et al., 2016b), and these features address a breadth of writing sub-constructs (including use of sources, claims, and evidence; topic development; coherence; and knowledge of English conventions). Through an optional entry survey, WM collects self-efficacy data about writing and English language status from users. Tool perceptions are collected from users through an optional exit survey. Informed by language arts models consistent with the Common Core State Standards Initiative and valued by the writing studies community, WM takes initial steps to integrate the reading and writing process by offering a range of textual features, including vocabulary support, intended to help users to understand unfamiliar vocabulary in coursework reading texts. This paper describes WM and provides discussion of descriptive evaluations from an Amazon Mechanical Turk (AMT) usability task situated in WM and from users-in-the-wild data. The paper concludes with a framework for developing writing feedback and analytics technology.