The way to describe this in OpenAPI, is to mark that field as **required**, because it will always be there.

Because of that, the JSON Schema for a model can be different depending on if it's used for **input or output**:

* for **input** the `description` will **not be required**
* for **output** it will be **required** (and possibly `None`, or in JSON terms, `null`)

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: bool | None = None


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: str | None = None):
    return {"item_id": item_id, "q": q}


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):

/// note | Nota

O FastAPI saberá que o valor de `q` não é obrigatório por causa do valor padrão `= None`.

O `str | None` não é utilizado pelo FastAPI para determinar que o valor não é obrigatório, ele saberá que não é obrigatório porque tem um valor padrão `= None`.

Mas adicionar as anotações de tipo permitirá ao seu editor oferecer um suporte melhor e detectar erros.

///

        summary: str | None = None,
        description: str | None = None,
        response_description: str = "Successful Response",
        responses: dict[int | str, dict[str, Any]] | None = None,
        deprecated: bool | None = None,
        methods: list[str] | None = None,
        operation_id: str | None = None,
        response_model_include: IncEx | None = None,

from fastapi.dependencies.utils import get_typed_annotation


def test_get_typed_annotation():
    # For coverage
    annotation = "None"
    typed_annotation = get_typed_annotation(annotation, globals())

from fastapi import Cookie, FastAPI

app = FastAPI()


@app.get("/items/")
async def read_items(ads_id: str | None = Cookie(default=None)):

Tu modelo de response podría tener valores por defecto, como:

{* ../../docs_src/response_model/tutorial004_py310.py hl[9,11:12] *}

* `description: Union[str, None] = None` (o `str | None = None` en Python 3.10) tiene un valor por defecto de `None`.
* `tax: float = 10.5` tiene un valor por defecto de `10.5`.
* `tags: List[str] = []` tiene un valor por defecto de una list vacía: `[]`.

class DummyClient:
    async def get_people(self) -> list:
        return ["John Doe", "Jane Doe"]

    async def close(self) -> None:
        pass


async def get_client() -> AsyncGenerator[DummyClient, None]:
    client = DummyClient()
    yield client
    await client.close()


Client = Annotated[DummyClient, Depends(get_client)]


@pytest.fixture(name="client")

from fastapi import FastAPI

app = FastAPI()


@app.get("/items/")
async def read_items(q: str | None = None):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

bucket # - name: bucket1 # # Policy to be set on the # # bucket [none|download|upload|public] # policy: none # # Purge if bucket exists already # purge: false # # set versioning for # # bucket [true|false] # versioning: false # remove this key if you do not want versioning feature # # set objectlocking for # # bucket [true|false] NOTE: versioning is enabled by default if you use locking # objectlocking: false # - name: bucket2 # policy: none # purge: false # versioning: true # # set objectlocking for...