Pydantic

Most PDF extraction projects start with the document. You open a PDF, look at the text, write a regex, extract a value. Repeat for each field. This works for one document type with one layout. It doesn’t scale. Schema-first extraction inverts the order: define exactly what the output should look like before you write a single line of extraction code. The schema becomes the specification that every extraction function has to satisfy — and the tool that tells you, immediately and explicitly, when an extraction fails.