Software for Exportable NURBS surfaces from Parametric Equations $x=f(u, v), y=f(u, v), z=f(u, v)$ (Must be Suitable for Engineering)

Question

The title pretty much says it all. Is there any software out there that lets you input 3D parametric equations without having to go to the trouble of writing a bunch of code and then lets you export to STEP or Parasolid?

I need the output to be equivalent to what you'd get from CAD software, i.e., the ability to set tolerances, etc.., for a final export surface that meets quality/accuracy specifications.

Thanks in advance.