Safety-critical software-dependent systems such as those found in the avionics, automotive, maritime, and energy domains often need to be certified by a licensing or regulatory body based on one or more safety standards. Safety standards do not specify the details of the evidence that needs to be collected for the certification of a particular system because these standards need to be generalizable and applicable to a wide variety of systems. Without an upfront agreement between the system supplier and the certifier about the details of the evidence that needs to be collected, there will invariably be important omissions in the evidence information provided by the supplier, which will need to be remedied after the fact and at significant costs. The contributions of this article are twofold: we present both a flexible approach and a publicly available supporting tool for assisting suppliers and certifiers in developing an agreement about the evidence necessary to demonstrate compliance to a safety standard. The approach is model-based; specifically, the safety standard of interest is expressed via an information model. The supporting tool, which is available online, takes this information model as input and assists system suppliers and the certifiers in reaching a documented and consistent agreement about the safety evidence that needs to be collected.