  We compute six-point string amplitudes for the scattering of one closed
string Ramond-Ramond state, two tachyons, and two gauge fields in the
worldvolume of D-brane-anti-D-brane systems in the Type II superstring
theories. From the resulting S-matrix elements, we read off the precise form of
the couplings, including their exact numerical coefficients, of two tachyons
and two gauge fields in the corresponding highly symmetric effective field
theory (EFT) Lagrangian in the worldvolume of D-brane-Anti-D-brane to all
orders in $\alpha'$, which modify and complete previous proposals. We verify
that the EFT reproduces the infinite collection of stringy gauge field
singularities in dual channels. Inspired by interesting similarities between
the all-order highly symmetric EFTs and holographic duals of Vasiliev's higher
spin gravities \`a l\`a Nilsson and Vasiliev, we make a proposal for
tensionless limits of D-brane-anti-D-brane systems.
