The present research evaluated the usability of the SHAD application in mobile learning from two complementary perspectives: "Pedagogical Usability" and "User Interface Usability." This applied study utilized a "Mixed Methods Sequential Explanatory Design." In the quantitative phase, descriptive-survey and correlational methods were employed with a census of all 276 primary school teachers in Khalkhal (2024-2025). In the qualitative phase, to further explain the quantitative findings, semi-structured interviews were conducted with 8 purposively selected experts. Data were collected using the standard CECAM questionnaire (Navarro et al., 2024) and semi-structured interviews. Analysis involved one-sample t-tests, Structural Equation Modeling (to confirm measurement and structural models), and thematic analysis. Findings indicate a dual nature of usability; SHAD performed above average in "Design," "Navigation," "Customization" (UI), and "Social Interaction" (Pedagogical). Conversely, it faced significant weaknesses in "Personalization," "Activities," "Multimedia," "Content" (Pedagogical), and "Feedback" (UI). Qualitative findings explained that these weaknesses stem from challenges such as "inflexibility of the learning path," "lack of systemic and immediate feedback," "passive nature of tasks," "aesthetic poverty," and "weakness in message design." Results suggest that to become an effective learning tool, SHAD requires a strategic revision in its pedagogical capabilities. Given the sample limitation to one region, the generalization of results should be approached with caution.