  In this short note we clarify the role of the boundary terms in the
calculation of the leading order tree-level bispectrum in a fairly general
minimally coupled single field inflationary model, where the inflaton's
Lagrangian is a general function of the scalar field and its first derivatives.
This includes k-inflation, DBI-inflation and standard kinetic term inflation as
particular cases. These boundary terms appear when simplifying the third order
action by using integrations by parts. We perform the calculation in the
comoving gauge obtaining explicitly all total time derivative interactions and
show that a priori they cannot be neglected. The final result for the
bispectrum is equal to the result present in the literature which was obtained
using the field redefinition.
