The tools working group in the MPI forum is currently in the process of finishing a specification for a new tool interface in MPI-3. This new API, called the MPIT interface, will allow MPI implementations to offer internal performance information, such as queue length, memory allocations, or timings for message processing. Tools can query which type of information is offered by a particular MPI implementation and read the data offered in a similar manner as performance counters offered through interfaces like PAPI. This talk will give an overview of the MPIT interface and its capabilities and is intended to encourage feedback on its design.