BackgroundThere is a need for medical education on health care transitions for youth with special health care needs. The Texas Transition Toolkit (the tool) supports providers through a one-stop shop for researching literature on care transitions, a catalog of care transition tools, and guides for developing care transition programs.ObjectiveThis study aims to assess the functionality and usability of the tool with providers working with transition-aged children and youth with special health care needs (representative users).MethodsThe tool was evaluated using a triangulated mixed methods case study approach consisting of a concurrent think-aloud phase, a satisfaction survey, and a survey of problem relevance and task performance to operationalize and capture functionality and usability. Our mixed methods deep dive into the functionality and usability of the tool focused on 10 representative users from one medical home in Texas and 5 website design experts.ResultsRepresentative users found the tool to be highly relevant, as demonstrated by the satisfaction score for relevance (138/150, 92%). According to the users, the tool provided comprehensive information related to health care transitions for youth with special health care needs, with a satisfaction score of 87.3% (131/150) for comprehensive. Overall satisfaction with the tool was high at 81.92% (1065/1300) with a cutoff score of 73.33% (953.4/1300) indicating high satisfaction, but users reported relatively lower satisfaction with search (114/150, 76%) and navigation (ease of use: 114/150, 76%; hyperlinks: 163/200, 81.5%; structure: 159/200, 79.5%). They experienced search- and navigation-related problems (total problems detected: 21/31, 68%) and, based on quality checks, had a relatively low task completion rate for tasks involving finding information (60/80, 75%), which required searching and navigation. The problems identified around search and navigation functionality were relevant (relevance scores ranging from 14.5 to 22, with a cutoff score of 11.7 indicating relevance).ConclusionsThe tool may help bridge the gaps in training on health care transitions for youth with special health care needs in US medical education. The tool can be used to create structured protocols to help improve provider knowledge, collaboration across pediatric and adult care providers, and the continuity of care as youth with special health care needs transition from pediatric to adult care. The results provided a road map for optimizing the tool and highlighted the importance of evaluating eHealth technologies with representative users.