x_trace: str = Header(default=..., title="Tracing header"),
):
    return {"message": "Hello World"}
```

...all these parameters are required because the default value is `...` (Ellipsis).

But now it's possible and supported to just omit the default value, as would be done with Pydantic fields, and the parameters would still be required.

✨ For example, this is now supported:

```Python