We present a construction of an open analogue of total descendant and total ancestor potentials via an "open version" of Givental's action. Our construction gives a genus expansion for an arbitrary solution to the open WDVV equations satisfying a semisimplicity condition and admitting a unit. We show that the open total descendant potentials we define satisfy the open topological recursion relations in genus 0 and 1, the open string and open dilaton equations. Contents 1. Introduction 1 2. A Givental-type theory for solutions to the open WDVV equations 6 3. Open total descendant potentials 17 4. Proof of Theorem 2 22 References 27 *Applying to the pair, ε) a certain shift, a linear change of variables, and the G o N +1,+ -action, we obtain a space of pairs (F c,anc , F o,anc ), where F c,anc is a closed total ancestor potential, and F o,anc is a new function, which we call an open total ancestor potential.