During the past few years much effort has been put into developing interoperable grid models suitable of defining a decentralized control setting. Such environments may define new rules and actions to internal Virtual Organisation (VO) members and therefore posing new challenges towards to an extended cooperation model of grids. Particularly, VO members' knowledge may be expressed in the form of intelligent agents thus providing a more autonomous solution of communicating members. Herein we present a mobile agent middleware for Grid interoperable infrastructures. Facing the enlarging scale of Grid, the proposed middleware aims to extend the knowledge of a specific neighbouring of Grid members (VO) in relation to the addresses and the physical resources of known and unknown nodes which may join the Grid VO. The internal data are structured in a rational sequence and stored within a public profile of each member called metadata snapshot profile. The middleware is designed by employing the Java Agent Development (JADE) framework in which mobile agents are travelling throughout the domain and by collecting and updating internal data they extend the size of the VO. The interoperable standard is achieved by using the Critical Friends Community (CFC) model, as the mean to fulfil the inter-cooperation model.