  Elaborating on the novel formulation of the loop-tree duality, we introduce
the Mathematica package Lotty that automates the latter at multi-loop level. By
studying the features of Lotty and recalling former studies, we discuss that
the representation of any multi-loop amplitude can be brought in a form, at
integrand level, that only displays physical information, which we refer to as
the causal representation of multi-loop Feynman integrands. In order to
elucidate the role of Lotty in this automation, we recall results obtained for
the calculation of the dual representation of integrands up-to four loops.
Likewise, within Lotty framework, we provide support to the all-loop causal
representation recently conjectured by the same author. The numerical stability
of the integrands generated by Lotty is studied in two-loop planar and
non-planar topologies, where a numerical integration is performed and compared
with known results.
