The OECD QSAR Toolbox is a software designed to support hazard assessment of chemicals as well as to increase mechanistic and other knowledge on chemical substances in a cost-efficient way. As a freely available computational tool, it promotes the use of assessment methods alternative to animals and minimizes unnecessary animal testing without reducing the safety of human health and environment. It is intended to be used by governments, chemical industry and other stakeholders.
The OECD QSAR Toolbox is a good software to predict the mutagenicity of compounds without charge under ICH M7. Lots of information is available from it, while it requires user training due to its multiple functions. From the point of a light user, paid (Q)SAR software that supports nitrosamine prediction is more user-friendly.
I use QSAR Toolbox pretty extensively in my work. It is pretty simple to use and there are extensive tutorials on the site itself. For regulatory submissions, a Toolbox analysis does not work as a stand-alone, but it does add to the weight of evidence when included in a risk assessment.