I took a crack at updating the spec with additional explanations and examples. Let me know if that makes things clearer. I don't think it makes sense to document the full implementation of these decorator functions or metaclasses in the spec. They're quite complex. For example, here's an implementation of the `@dataclass` decorator function: https://github.com/ericvsmith/dataclasses/blob/95d2a4ca30e9dfdbc6837921cc5a5.... The implementations in `attrs`, `pydantic` and other libraries are similarly complex, but they're all doing roughly the same thing — synthesizing methods including an `__init__` method that includes one parameter for each declared data field. The phrase "dataclass semantics" is meant to refer to the behaviors listed in the "Motivation" section at the beginning of the spec. Additional details can be found in the subsection titled "Dataclass Semantics". -Eric -- Eric Traut Contributor to Pyright & Pylance Microsoft Corp.