The Modular Information Provider (MIP) has been developed to systematically aggregate multiple sources of information for Grid information services (GIS). MIP undertakes the challenge of mapping information from a large number of sources to information services with minimal human intervention. MIP addresses such mappings using a modular approach to achieve interoperability among Grid environments. MIP can be customized in a straightforward way to a specific Grid environment or information schema. Current MIP implementation is based on Globus MDS4 and the XML version of GLUE Schema 1.2. The design of MIP aims to address the shortcomings that exist in current Grid information providers (e.g., the Generic Information Provider) as well as to support web service-based GIS. Our modular approach has been developed to ease maintenance and management of Grid information systems by automatically aggregating information sources and providing appropriate pieces of information to GIS based on predefined information schemas. Upon installation, MIP is configured to set up only necessary modules, which minimizes memory usage.