The neutronics toolkit is a complete suite of codes that can support low- to high-fidelity neutronics analyses. The suite can be used to analyze a fast reactor's entire fuel cycle, including cross section generation, radiation transport, and fuel cycle modeling. MCC-3 code and Cross Section API generate high quality multi-group cross sections with spatial heterogeneity effects. PROTEUS is a finite-element-method based suite that features a nodal solver as well as two high-fidelity, massively-parallel neutron transport solver options (discrete ordinates and method of characteristics). These solvers are intended to cater to a broad spectrum of neutron physics calculation needs and offer unique deterministic analysis capabilities for advanced reactor designs with complex, unconventional geometries including the ability to model the multi-physics feedback effects due to geometric deformations. PERSENT code offers capabilities for perturbation and sensitivity analyses with the matching level of fidelity based on the variational nodal method solving the second-order even-parity transport equation. The toolkit also includes meshing tools for generation of unstructured finite element meshes for Cartesian and hexagonal lattice geometries and offers interoperability with other commercial mesh generation software. Post-processing and visualization capabilities based on open source VisIt application.