AnkiDroid has its own JS API that provides some functionality unavailable on other platforms. I don’t think it has the capability to modify card data though, but I don’t follow its development closely, so you might want to take a look in case I’m missing something or the doc is incomplete.
AnkiMobile, on the other hand, is likely to be completely out of the question in this regard.
As far as I’m aware, API PRs are not very likely to get accepted at this point[1][2][3]. Especially the functionality that involves access to the database for the security risks involved[4].