{!> ../../../docs_src/generate_clients/tutorial002_py39.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="23  28  36"
    {!> ../../../docs_src/generate_clients/tutorial002.py!}
    ```

### Generate a TypeScript Client with Tags

If you generate a client for a FastAPI app using tags, it will normally also separate the client code based on the tags.

                    self._type_adapter.validate_python(value, from_attributes=True),
                    None,
                )
            except ValidationError as exc:
                return None, _regenerate_error_with_loc(
                    errors=exc.errors(include_url=False), loc_prefix=loc
                )

        def serialize(
            self,
            value: Any,
            *,

    Type,
    Union,
    cast,
)

import anyio
from fastapi import params
from fastapi._compat import (
    PYDANTIC_V2,
    ErrorWrapper,
    ModelField,
    Required,
    Undefined,
    _regenerate_error_with_loc,
    copy_field_info,
    create_body_model,
    evaluate_forwardref,
    field_annotation_is_scalar,
    get_annotation_from_field_info,
    get_missing_field_error,
    is_bytes_field,

    new_field.populate_validators()  # type: ignore[attr-defined]
    return new_field


def generate_operation_id_for_path(
    *, name: str, path: str, method: str
) -> str:  # pragma: nocover
    warnings.warn(
        "fastapi.utils.generate_operation_id_for_path() was deprecated, "
        "it is not used internally, and will be removed soon",
        DeprecationWarning,

It's relatively tightly coupled with relational databases (like MySQL or PostgreSQL), so, having a NoSQL database (like Couchbase, MongoDB, Cassandra, etc) as the main store engine is not very easy.

It was created to generate the HTML in the backend, not to create APIs used by a modern frontend (like React, Vue.js and Angular) or by other systems (like <abbr title="Internet of Things">IoT</abbr> devices) communicating with it.

            """
        ),
    ] = ...,
    *,
    default_factory: Annotated[
        Union[Callable[[], Any], None],
        Doc(
            """
            A callable to generate the default value.

            This doesn't affect `Path` parameters as the value is always required.
            The parameter is available only for compatibility.
            """
        ),
    ] = _Unset,

For example:

```Python hl_lines="4-7"
{!../../../docs_src/behind_a_proxy/tutorial003.py!}
```

Will generate an OpenAPI schema like:

```JSON hl_lines="5-7"
{
    "openapi": "3.1.0",
    // More stuff here
    "servers": [
        {
            "url": "/api/v1"
        },
        {

And there are dozens of alternatives, all based on OpenAPI. You could easily add any of those alternatives to your application built with **FastAPI**.

You could also use it to generate code automatically, for clients that communicate with your API. For example, frontend, mobile or IoT applications.

## Recap, step by step

### Step 1: import `FastAPI`

```Python hl_lines="1"

If you want to play with JWT tokens and see how they work, check <a href="https://jwt.io/" class="external-link" target="_blank">https://jwt.io</a>.

## Install `python-jose`

We need to install `python-jose` to generate and verify the JWT tokens in Python:

<div class="termy">

```console
$ pip install "python-jose[cryptography]"

---> 100%
```

</div>

```

In this example, the *path operations* under the `router` will use the custom `TimedRoute` class, and will have an extra `X-Response-Time` header in the response with the time it took to generate the response:

```Python hl_lines="13-20"
{!../../../docs_src/custom_request_and_route/tutorial003.py!}