In grids, many control subsystems are implemented by group of distributed agents that need to be coordinated and synchronised. In this paper we present a tool that implements a coordination protocol based on a generic, extensible and personalisable token passing protocol. We show how this tool performs different types of synchronisation tasks in a real Grid testbed. The Grid coordination protocol (GCP) is described, then its implementation, validation and usage, in the context of the European DataGrid project, are presented. We illustrate how GCP is used for network performance measurement coordination, for monitoring equipment configuration synchronisation and also for Grid network topology discovery operations.