If something else fail, e.g. as you mentioned some includes from the internals are missing (core, util, formulas, etc.) then this is a bug and you can create an issue or prepare pull request at GitHub (https://github.com/boostorg/geometry).

It is definitely the case that simply including (and not even using) is_valid.hpp fails because it requires core/cs.hpp for a definition of cs_tag.  Do you need a bug report for that?