I have great respect for your work with FastAPI and Typer, the latter of which I’m an avid user of, and you’ve inspired me to use type annotations for run-time use in my own code. However, I’m not a fan of this proposal for reasons that have already been brought up (mostly that it adds information in one of the most information dense parts of a function definition). It mirrors my least favorite part of Typer, that the help text goes right next to the parameters in the function header (not saying it’s a bad design choice, I honestly can’t think of any other way to do it). I think it’s ok in Typer, even if it makes working on documentation harder IMO, but I would not want to see that on the regular in other code.
For those wanting to discuss how the stdlib could be used to get the same information out of docstrings, I started a new topic. I see such an API as orthogonal to PEP 727, which would codify the existing approach to documentation.