The concept of 15-minute cities, aiming for accessible amenities within a short walk, has gained traction. In Korea, Chrono-Urbanism supports walkable neighborhood planning where essential services align with residents' living spaces. By evaluating walkability, bike accessibility, and transit, this study develops a FOSS4G-based tool for urban amenity distribution. The tool integrates multiple accessibility aspects to determine optimal urban amenity locations, using a network-based approach to minimize travel costs. It's designed using QGIS and Python, considering resident population, existing amenities, and urban environment. The tool's application assists officials, planners, and researchers in 15-minute city projects, identifying amenity needs, enhancing walkability, and aiding sustainable urban development. By leveraging FOSS4G, this tool promotes data-driven amenity placement, encourages sustainable transportation, and contributes to equitable urban development. It aligns with the 15-minute city vision, enhancing citizens' quality of life and fostering transparency and collaboration between planners and the public.