What are the key specifications and parameters of a potentiostat?

Devices that are as complex as a potentiostat have many different specifications and parameters listed in their documentation.

The first parameters to look at are the potential range and the current range. The currents and voltages, you want to apply and measure, must be within the capabilities of the instrument.

If you already know the values you want to use during the measurement, check if there is a list of extreme values for the technique you intend to use, for example, if you want to perform cyclic voltammetry with a scan rate of 10 V/s check the highest scan rate for cyclic voltammetry.

You should also check if the instrument supports the techniques you intend to use. Please note: Different instrument manufacturers sometimes use different terminologies for the same measurement techniques.

For Electrochemical Impedance Spectroscopy (EIS) check the frequency range and accuracy contour plot to make sure that the instrument is accurate in the frequency and impedance range you intend to use.

Some parameters are explained in detail here.