Why Annotated[str, T] doesn't work while Annotated[T, str] works well?

I have a project where user need to use Annotated[str, MyType()] a lot. In order to simplify it, I try to create a generic type

T = TypeVar('T')CustomUrl = Annotated[str, T]

But I get this error when I try to use it this way:

CustomUrl[MyData()]# TypeError: typing.Annotated[str, ~T] is not a generic class

I have no idea why this happens, and it works well when I reverse the order to

CustomUrl[T, str]

But that's not what I want. Is there any way to make it work?

My use case is to have user declare a dataclass and it will generate a UI schema automatically, for example

# pseudo code@dataclassclass TaskArgs:  input_text: Annotated[str, {'multiline': True}]  input_file: Annotated[str, {'multifiles': True}]

Update

I have try the following answer:

from typing import Annotated, TypeVarT = TypeVar('T')class CustomeUrl(Annotated[str, T]):    ...c: CustomeUrl = 's'

The problem is the last expression raise the error:

Expression of type "Literal['s']" is incompatible with declared type "CustomeUrl""Literal['s']" is incompatible with "CustomeUrl"

The reason I choose Annotated is to ensure the type check is valid so I don't think it solves my issue.