We are developing a portable integrated tool environment, called "Annai", for distributed memory parallel processors (DMPPs), as part of the joint CSCS-ETH/NEC collaboration in parallel processing. As we design and implement a sequence of tool prototypes, these are used and evaluated by a team of application developers. This close interaction allows rapid feedback, as requests from the application developers for functionality enhancements can be promptly considered for inclusion in future tool designs and prototypes. Our tool environment consists of an extended High Performance Fortran (HPF) compiler, a performance monitor and analyzer and a source-level debugger for distributed programs, all sharing a common user interface. The recently-defined Message Passing Interface (MPI) serves as our low-level machine interface and allows portability independent of the target hardware architecture. The key features of the tool environment comprise HPF language extensions to allow dynamic data distributions, and support for both high-level data-parallel and low-level message-passing programming paradigms by the interactive debugger and the interactive performance monitor and analyzer. The language extensions are particularly useful for the efficient parallelization of unstructured problems, and they are fully supported by both the debugger and the performance analyzer. We outline the structure of the tool environment, and summarize the functionality of its components. We also demonstrate an example user session and present performance results on two DMPPs.