  We provide the covariant superspace equations that are sufficient to
determine the complete $\theta$ expansion of the vertex operator of the open
string massive states with $(mass)^2=1/\alpha'$ in pure spinor formalism of
superstring theory. These equations get rid of the redundant degrees of freedom
in superfields and are consistent with the BRST conditions derived in [1].
Further, we give the explicit $\theta$ expansion of the superfields appearing
in the unintegrated vertex to $O(\theta^3)$. Finally, we compute the
contribution to a 3-point tree amplitude with the resulting vertex operator
upto $O(\theta^3)$ and find its kinematic structure to be identical to the
corresponding RNS computation.
