Context : StePar is an automatic code written in Python 3.X designed to compute the stellar atmospheric parameters T _ { eff } , \log { g } , [ Fe/H ] , and \xi of FGK-type stars by means of the EW method .
This code has already been extensively tested in different spectroscopic studies of FGK-type stars with several spectrographs and against myriads of Gaia-ESO Survey UVES U580 spectra of late-type , low-mass stars as one of its thirteen pipelines .

Aims : We describe the code and test it against a library of well characterised Gaia benchmark stars .
We also release the code to the community and provide the link for download .

Methods : We carried out the required EW determination of { Fe \textsc { i } } and { Fe \textsc { ii } } spectral lines using the automatic tool TAME . StePar implements a grid of MARCS model atmospheres and the MOOG radiative transfer code to compute stellar atmospheric parameters by means of a Downhill Simplex minimisation algorithm .

Results : We show the results of the benchmark star test and also discuss the limitations of the EW method , and hence the code .
In addition , we found a small internal scatter for the benchmark stars of 9 \pm 32 K in T _ { eff } , 0.00 \pm 0.07 dex in \log { g } , and 0.00 \pm 0.03 dex in [ Fe/H ] .
Finally , we advise against using StePar on double-lined spectroscopic binaries or spectra with R ¡ 30,000 , { SNR } ~ { } < ~ { } 20 or v \sin { i } ~ { } > 15 ~ { } { km~ { } s } ^ { -1 } as well as stars later than K4 or earlier than F6 .

Conclusions :