  We present a detailed assessment of uncertainties in parton-to-pion and
parton-to-kaon fragmentation functions obtained in recent global QCD analyses
of single-inclusive hadron production data at next-to-leading order accuracy.
We use the robust Lagrange multiplier approach for determining uncertainties to
validate the applicability of the simpler but approximate Hessian method.
Extensive comparisons of the results obtained within both methods are presented
for the individual parton-to-pion and kaon fragmentation functions. We provide
Hessian eigenvector sets of pion and kaon fragmentation functions that allow
one to easily propagate their uncertainties to any observable. Various
applications of these sets are presented for pion and kaon production in
electron-positron annihilation, lepton-nucleon scattering, and proton-proton
collisions.
