Human-Computer Interaction (HCI) plays a critical role in software systems, especially when targeting vulnerable individuals (e.g., assistive technologies). However, there exists a gap between well-tooled software development methodologies and HCI techniques, which are generally isolated from the development toolchain and require specific expertise. In this paper, we propose a human-driven software development methodology making User Interface (UI) a full-fledged dimension of software design. To make this methodology useful in practice, a UI design language and a user modeling language are integrated into a tool suite that guides the stakeholders during the development process, while ensuring the conformance between the UI design and its implementation.