{
    "responses": {
        "404": {
            "description": "Additional Response",
            "content": {
                "application/json": {
                    "schema": {
                        "$ref": "#/components/schemas/Message"
                    }
                }
            }
        },
        "200": {
            "description": "Successful Response",
            "content": {

### OpenAPI

**FastAPI** generates a "schema" with all your API using the **OpenAPI** standard for defining APIs.

#### "Schema"

A "schema" is a definition or description of something. Not the code that implements it, but just an abstract description.

#### API "schema"

    ```

=== "Python 3.8+"

    ```Python hl_lines="20-21"
    {!> ../../../docs_src/path_operation_configuration/tutorial003.py!}
    ```

## Description from docstring

### OpenAPI

**FastAPI** génère un "schéma" contenant toute votre API dans le standard de définition d'API **OpenAPI**.

#### "Schéma"

Un "schéma" est une définition ou une description de quelque chose. Pas le code qui l'implémente, uniquement une description abstraite.

#### "Schéma" d'API

* `description`: a `str` with a short description for the tag. It can have Markdown and will be shown in the docs UI.
* `externalDocs`: a `dict` describing external documentation with:
    * `description`: a `str` with a short description for the external docs.
    * `url` (**required**): a `str` with the URL for the external documentation.

from fastapi import FastAPI, Security
from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
from fastapi.testclient import TestClient

app = FastAPI()

security = HTTPBearer(description="HTTP Bearer token scheme")


@app.get("/users/me")
def read_current_user(credentials: HTTPAuthorizationCredentials = Security(security)):
    return {"scheme": credentials.scheme, "credentials": credentials.credentials}

from fastapi import FastAPI, Security
from fastapi.security import HTTPAuthorizationCredentials, HTTPDigest
from fastapi.testclient import TestClient

app = FastAPI()

security = HTTPDigest(description="HTTPDigest scheme")


@app.get("/users/me")
def read_current_user(credentials: HTTPAuthorizationCredentials = Security(security)):
    return {"scheme": credentials.scheme, "credentials": credentials.credentials}


client = TestClient(app)

from fastapi import Depends, FastAPI, Security
from fastapi.security import APIKeyQuery
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

api_key = APIKeyQuery(name="key", description="API Key Query")


class User(BaseModel):
    username: str


def get_current_user(oauth_header: str = Security(api_key)):
    user = User(username=oauth_header)
    return user


@app.get("/users/me")

                        },
                        "500": {"description": "Server error level 0"},
                        "501": {"description": "Server error level 1"},
                        "502": {"description": "Server error level 2"},
                        "503": {"description": "Server error level 3"},
                        "504": {"description": "Server error level 4"},

                    "required": IsOneOf(
                        ["description", "type", "size"],
                        # TODO: remove when deprecating Pydantic v1
                        ["description", "size"],
                    ),
                    "type": "object",
                    "properties": {
                        "description": {"title": "Description", "type": "string"},