I think it is reasonable to ask for capacitance and inductance measurements. This is useful for determining compatibility with electronics, particularly for longer cables.
I also find it useful to know the conductor material and primary insulation material (the insulation used on the primary conductors). While I wouldn't necessarily rule out a cable that used an unusual dielectric material, I'm more likely to try out a cable if I know it uses PFTE or FEP insulation since I have some experience in they way they sound.
For speaker cable or power cords, it's also helpful to know the effective wire gauge, particularly for longer runs.
I also find it useful to know the conductor material and primary insulation material (the insulation used on the primary conductors). While I wouldn't necessarily rule out a cable that used an unusual dielectric material, I'm more likely to try out a cable if I know it uses PFTE or FEP insulation since I have some experience in they way they sound.
For speaker cable or power cords, it's also helpful to know the effective wire gauge, particularly for longer runs.