You will see the JSON response as:

```JSON
{"message": "Hello World"}
```

### Interactive API docs

Now go to <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

You will see the automatic interactive API documentation (provided by <a href="https://github.com/swagger-api/swagger-ui" class="external-link" target="_blank">Swagger UI</a>):

documentation générée automatiquement et interactive :

<img src="/img/tutorial/path-params/image01.png">

!!! info
    À nouveau, en utilisant uniquement les déclarations de type Python, **FastAPI** vous fournit automatiquement une documentation interactive (via Swagger UI).

    On voit bien dans la documentation que `item_id` est déclaré comme entier.

## Déclarer des métadonnées supplémentaires

On peut aussi ajouter plus d'informations sur le paramètre.

Ces informations seront incluses dans le schéma `OpenAPI` généré et utilisées par la documentation interactive ou les outils externes utilisés.

!!! note
    Gardez en tête que les outils externes utilisés ne supportent pas forcément tous parfaitement OpenAPI.

When you see the automatic docs, you can check that the input model and output model will both have their own JSON Schema:

<img src="/img/tutorial/response-model/image01.png">

And both models will be used for the interactive API documentation:

<img src="/img/tutorial/response-model/image02.png">

## Other Return Type Annotations

### Documentation API interactive

Maintenant, rendez-vous sur <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

Vous verrez la documentation interactive automatique de l'API (fournie par <a href="https://github.com/swagger-api/swagger-ui" class="external-link" target="_blank">Swagger UI</a>) :

* `/items/`
* `/items/{item_id}`

...as we intended.

* They will be marked with a list of tags that contain a single string `"items"`.
    * These "tags" are especially useful for the automatic interactive documentation systems (using OpenAPI).
* All of them will include the predefined `responses`.
* All these *path operations* will have the list of `dependencies` evaluated/executed before them.

* **Validate data**: coming from each request:
    * Generating **automatic errors** returned to the client when the data is invalid.
* **Document** the API using OpenAPI:
    * which is then used by the automatic interactive documentation user interfaces.

This might all sound abstract. Don't worry. You'll see all this in action in the [Tutorial - User Guide](tutorial/index.md){.internal-link target=_blank}.

* Convertirà *da* e *a* JSON automaticamente.
* Documenterà tutto con OpenAPI, che può essere usato per:
    * Sistemi di documentazione interattivi.
    * Sistemi di generazione di codice dal lato client, per molti linguaggi.
* Fornirà 2 interfacce di documentazione dell'API interattive.

---

Questa è solo la punta dell'iceberg, ma dovresti avere già un'idea di come il tutto funzioni.

* The _path_ `/items/{item_id}` has an optional `str` _query parameter_ `q`.

### Interactive API docs

Now go to <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

You will see the automatic interactive API documentation (provided by <a href="https://github.com/swagger-api/swagger-ui" class="external-link" target="_blank">Swagger UI</a>):

* The _path_ `/items/{item_id}` has an optional `str` _query parameter_ `q`.

### Interactive API docs

Now go to <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

You will see the automatic interactive API documentation (provided by <a href="https://github.com/swagger-api/swagger-ui" class="external-link" target="_blank">Swagger UI</a>):