  The search for twins of the Sun and Earth relies on accurate characterization
of stellar and exoplanetary parameters: i.e., ages, masses, and radii. In the
modern era of asteroseismology, parameters of solar-like stars are derived by
fitting theoretical models to observational data, which include measurements of
their oscillation frequencies, metallicity [Fe/H], and effective temperature
Teff. Combining this information with transit data furthermore yields the
corresponding parameters for their exoplanets. While [Fe/H] and Teff are
commonly stated to a precision of ~0.1 dex and ~100 K, the impact of errors in
their measurement has not been studied in practice within the context of the
parameters derived from them. Here we use the Stellar Parameters in an Instant
(SPI) pipeline to estimate the parameters of nearly 100 stars observed by
Kepler and Gaia, many of which are confirmed planet hosts. We adjust the
reported spectroscopic measurements of these stars by introducing faux
systematic errors and artificially increasing the reported uncertainties, and
quantify the differences in the resulting parameters. We find that a systematic
error of 0.1 dex in [Fe/H] translates to differences of only 4%, 2%, and 1% on
average in the resulting stellar ages, masses, and radii, which are well within
their uncertainties (~11%, 3.5%, 1.4%) as derived by SPI. We also find that
increasing the uncertainty of [Fe/H] measurements by 0.1 dex increases the
uncertainties by only 0.01 Gyr, 0.02 M_sun, and 0.01 R_sun, which are again
well below their reported uncertainties (0.5 Gyr, 0.04 M_sun, 0.02 R_sun). The
results for Teff at 100 K are similar. Stellar parameters from SPI are
unchanged within uncertainties by errors of up to 0.14 dex or 175 K, and are
even more robust to errors in Teff than the seismic scaling relations.
Consequently, the parameters for their exoplanets are robust as well.
