This study evaluates a “feedback-only,” constrained-generative AI tool designed to support revision without generating or rewriting student text. StoryCoach was developed for a business communication elective and grounded in cognitive apprenticeship with principles of feedback literacy. The tool generated structured feedback: one strength, one opportunity, and one reflective question per submission. Analysis of 57 paired drafts showed significant gains in feature-specific rhetorical execution, with vividness as the primary quantitative indicator (Cohen’s d  = 1.39), supported by independent reader judgments and student reflections. Findings demonstrate that constrained-generative AI can function as a pedagogical partner that strengthens rhetorical awareness and preserves authorship integrity.