I'm not going to call it good, but I used to use FDF (forms data format) along with pdftk to fill in PDF files on the command line using a combination of Makefiles, pdfs, and fdfs. Here's the best reference I could find for the "standard":
https://www.iso.org/obp/ui/#iso:std:iso:19444:-1:ed-1:v1:en
That said, the workflow was pretty terrible. Basically, I had to use pdftk to output from the pdf what fields were writable. Some forms like from the IRS, were pretty good at labeling things. Most other forms were terrible and there was a lot of guessing and checking. As such, this doesn't exactly answer your question, but more to comment that there was sort of a way, kind of.