In this paper we are introducing SimTools, a simple way to create tools with well-defined inputs and outputs. Ease-of-use is a priority; a SimTool is a Jupyter notebook which can be a self-contained simulation or a wrapper that calls a larger tool. Inputs and outputs are described in YAML embedded in the notebook. A new copy of the notebook is returned as the result of the run, with the cells showing the progress of the simulation, including intermediate results for debugging. Outputs are embedded in the notebook metadata as data or database references. Published SimTools can be deployed as Docker or Singularity images and will be runnable on any platform that can run those containers.
