Agents act and perceive in shared environments where they are situated. Although there are many environments for agents - ranging from testbeds to commercial applications - such environments have not been widely used because of the difficulty of interfacing agents with those environments. A more generic approach for connecting agents to environments would be beneficial for several reasons. It would facilitate reuse, comparison, the development of truly heterogeneous agent systems, and increase our understanding of the issues involved in the design of agent-environment interaction. To this end, we have designed and developed a generic environment interface standard. Our design has been guided by existing agent programming platforms. These platforms are not only suitable for developing agents but also already provide some support for connecting agents to environments. The interface standard itself is generic, however, and does not commit to any specific platform features. The interface proposal has been implemented and evaluated in a number of agent platforms. We aim at a de facto standard that might become an actual standard in the near future.