  Asymptotic Safety implies that observables including scattering amplitudes
remain finite at the highest energy scales. Traditionally, this feature is
connected to an interacting fixed point of the Wilsonian renormalization group
that provides the high-energy completion of the theory. In this article, we
discuss a different facet of Asymptotic Safety, reviewing its imprint on the
quantum effective action. We start with a concise introduction to the form
factor framework for gravity and gravity-matter systems, before giving an
encyclopaedic overview of gravity-mediated scattering amplitudes derived from
the quantum effective action. We illustrate the use of the framework based on
form factors appearing in the context of quadratic gravity and Asymptotic
Safety, before making the connections to positivity bounds derived for
low-energy effective field theories and the computation of form factors from
first principles. We conclude that the form factor framework offers a unique,
unifying perspective on quantum gravity. In particular, it plays a pivotal role
in determining the phenomenological consequences of Asymptotic Safety at the
level of observables.
