A Harvest App developer designs, builds, and maintains applications for the Harvest platform, a time-tracking and reporting software. They integrate Harvest's API into other software applications to streamline workflow and enhance productivity. Their responsibilities include understanding client requirements, developing application functionality, testing and debugging code, and ensuring user-friendly interfaces. They also troubleshoot issues and regularly update the application to improve performance and add new features. Furthermore, they collaborate with a team of developers, UI/UX designers, and project managers, while adhering to best coding practices and maintaining the security of sensitive data.