  We present the complete structure of the azimuthal dependences and
polarization observables for two-hadron production in $e^+e^-$ annihilation
processes within a transverse momentum dependent (TMD) approach adopting the
helicity formalism. The leading-twist TMD fragmentation functions (TMD-FFs) for
spin-1/2 hadrons are fully accounted for. The role of the polarizing FF,
together with its extraction from Belle data for the transverse polarization of
$\Lambda$'s, are discussed as well. Finally, predictions for SIDIS processes at
EIC are presented.
