Could you generalise that for is_hubbard:
false → GGA
true → GGA+U
Yes, this is correct. And if true, the specific U values should be in the hubbards dict. And currently, the only tasks we have are all PBE or PBE+U, no other functionals are currently present in our online database.
For a given structure, it’s also possible to re-generate the VASP inputs using pymatgen (specifically pymatgen.io.vasp.sets and MPRelaxSet, MPStaticSet etc.), so if you want to see why a specific U value was used etc., pymatgen is the place to look, or you can consult our documentation/papers.
We have gone through a very significant database schema change recently (see Significant release of new database schema and additional data) so if you do see anything from the REST endpoints that doesn’t seem to make sense, please do report it (and thank you for doing so!).