The evaluation of smart affordable cities considering sustainable subsystems improves urban quality of life through efficient resource usage, reduced environmental impacts, and improved living conditions for residents. This study aims to develop an interactive and dynamic Web Geographic Information System (GIS) framework to facilitate decision-making processes during the design phase while including third parties and stakeholders using a spatial interactive impact assessment approach. The methodology follows a quantitative research method based on delivering a tool that could be replicated in other contexts. This tool assesses the impact of smart scenarios to support affordable city planning through selecting Key Performance Indicators (KPIs). This tool was applied to Brazilian large-scale affordable housing within a smart city project. Based on this study, the conclusion reports some research limitations and the possibility of creating a beta version of the tool for future development. The findings show that this Web-GIS framework enhances stakeholder engagement and the effectiveness of decision making in developing sustainable urban planning.