This paper presents an ant-inspired algorithm for building a self-organizing information system of a Grid. Ant-inspired mobile agents travel the Grid through P2P (peer-to-peer) interconnections and disseminate "descriptors", i.e., metadata information about available Grid resources. Descriptors are reorganized and spatially sorted over the Grid, thus facilitating resource management and discovery. Moreover, agents distribute descriptors so as to respect the different capabilities of Grid hosts: hosts with higher storage capacity are assigned a larger number of descriptors than low capacity hosts. The effectiveness of the presented algorithm is assessed by event-driven simulation which proves that the simple operations performed by mobile agents successfully achieve both descriptor reorganization and fair load distribution.