The SIMPUT (SIMulation inPUT) file format developed by Schmid et al. (2013) is a FITS-based standard for handling source descriptions for simulations of astronomical observations. A SIMPUT file describes one or more sources by information about position, flux and energy spectrum as well as optional spatial flux distribution ("images") and timing information ("lightcurves"). A full description can be downloaded here.
This software package implements the basic features of the SIMPUT format, including tools to create simple SIMPUT files from the command line. It is part of the SIXTE software package. Please visit https://github.com/thdauser/sixte and the SIXTE homepage for more information and a tutorial on how to use the software.