Interface agents have specialized roles interacting with human users and provide communication channels between external and internal worlds of underlying information systems or within a multi-agent team. In this paper, we discuss the roles and functions of a Natural Language Enabled Interface Agent (NLEIA). We are particularly interested in integrating NLEIA with other agents within a multi-agent project team. The impact of having NLEIA on the overall performance and the usability of a complex software system in general and multi-agent team in particular will also be discussed. The paper starts with the background technologies for Natural Language Processing (NLP), which provide the implementation basis for NLEIA, followed with the description of roles and activities of NLEIA. Finally, several application examples demonstrating the feasibility of the proposed approach are presented.