called-interactively-p is a compiled Lisp function in `subr.el'.

(called-interactively-p KIND)

Return t if the containing function was called by `call-interactively'.
If KIND is `interactive', then only return t if the call was made
interactively by the user, i.e. not in `noninteractive' mode nor
when `executing-kbd-macro'.
If KIND is `any', on the other hand, it will return t for any kind of
interactive call, including being called as the binding of a key or
from a keyboard macro, even in `noninteractive' mode.

This function is very brittle, it may fail to return the intended result when
the code is debugged, advised, or instrumented in some form. Some macros and
special forms (such as `condition-case') may also sometimes wrap their bodies
in a `lambda', so any call to `called-interactively-p' from those bodies will
indicate whether that lambda (rather than the surrounding function) was called

Instead of using this function, it is cleaner and more reliable to give your
function an extra optional argument whose `interactive' spec specifies
non-nil unconditionally ("p" is a good way to do this), or via
(not (or executing-kbd-macro noninteractive)).

The only known proper use of `interactive' for KIND is in deciding
whether to display a helpful message, or how to display it. If you're
thinking of using it for any other purpose, it is quite likely that
you're making a mistake. Think: what do you want to do when the
command is called from a keyboard macro?