There has been a huge progress in implementing of new theoretical ideas to a large class of quantum field theories. One example, the BCFW recursion relations have been a very successful approach to tree-level amplitudes for Yang-Mills or gravity. Such modern methods cannot be typically used in effective field theories as the amplitudes do not exhibit the correct high-energy behaviour. However, we will discuss how the soft limits in case of scalar fields can be used as powerful constraints to fix the tree-level amplitudes. We will also briefly discuss how this allows to classify all interesting scalar effective field theories.
