{* ../../docs_src/path_operation_advanced_configuration/tutorial003.py hl[6] *}

## Advanced description from docstring { #advanced-description-from-docstring }

You can limit the lines used from the docstring of a *path operation function* for OpenAPI.

Adding an `\f` (an escaped "form feed" character) causes **FastAPI** to truncate the output used for OpenAPI at this point.

/* jcifs smb client library in Java
 * Copyright (C) 2000  "Michael B. Allen" <jcifs at samba dot org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,

* Validate that there is an `item_id` in the path for `GET` and `PUT` requests.
* Validate that the `item_id` is of type `int` for `GET` and `PUT` requests.
    * If it is not, the client will see a useful, clear error.
* Check if there is an optional query parameter named `q` (as in `http://127.0.0.1:8000/items/foo?q=somequery`) for `GET` requests.
    * As the `q` parameter is declared with `= None`, it is optional.

        this.append = false;
        this.smb2 = th.isSMB2();
        init(th);
    }

    /**
     * Initialize the output stream with the tree handle configuration.
     *
     * @param th the tree handle to use for configuration
     * @throws CIFSException if an error occurs during initialization
     */
    protected final void init(final SmbTreeHandleImpl th) throws CIFSException {

* **Convertir des données** : depuis la requête vers les types requis.
* **Valider des données** : venant de chaque requête :
    * Générant automatiquement des **erreurs** renvoyées au client quand la donnée est invalide.
* **Documenter** l'API avec OpenAPI :
    * ce qui ensuite utilisé par les interfaces utilisateur automatiques de documentation interactive.

                    appendJson("roles", entity.getRoles(), buf).append(',');
                    appendJson("user-agent", entity.getUserAgent(), buf).append(',');
                    appendJson("client-ip", entity.getClientIp(), buf).append(',');
                    appendJson("access-type", entity.getAccessType(), buf).append(',');
                    appendJson("query-time", entity.getQueryTime(), buf).append(',');

/* jcifs smb client library in Java
 * Copyright (C) 2000  "Michael B. Allen" <jcifs at samba dot org>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,

///

FastAPI will now:

* **Validate** the data making sure that the max length is 50 characters
* Show a **clear error** for the client when the data is not valid
* **Document** the parameter in the OpenAPI schema *path operation* (so it will show up in the **automatic docs UI**)

* **Daten umzuwandeln**: aus der Anfrage in den erforderlichen Typ.
* **Daten zu validieren**: aus jeder Anfrage:
    * **Automatische Fehler** generieren, die an den Client zurückgegeben werden, wenn die Daten ungültig sind.
* Die API mit OpenAPI zu **dokumentieren**:
    * Die dann von den Benutzeroberflächen der automatisch generierten interaktiven Dokumentation verwendet wird.

```

</div>

If you go to the `/docs` API UI, you will see that it is now updated, and it won't expect to receive the `id` from the client when creating a hero, etc.

<div class="screenshot">
<img src="/img/tutorial/sql-databases/image02.png">
</div>

## Recapitulando