# Extending OpenAPI

There are some cases where you might need to modify the generated OpenAPI schema.

In this section you will see how.

## The normal process

The normal (default) process, is as follows.

A `FastAPI` application (instance) has an `.openapi()` method that is expected to return the OpenAPI schema.

@app.put("/items/{item_id}")
async def update_item(
    *,
    item_id: int,
    item: Item = Body(
        openapi_examples={
            "normal": {
                "summary": "A normal example",
                "description": "A **normal** item works correctly.",
                "value": {
                    "name": "Foo",
                    "description": "A very nice Item",
                    "price": 35.4,

Prefer to use the `Annotated` version if possible.

///

```Python hl_lines="17"
{!> ../../docs_src/dependencies/tutorial006.py!}
```

////

These dependencies will be executed/solved the same way as normal dependencies. But their value (if they return any) won't be passed to your *path operation function*.

/// tip

Some editors check for unused function parameters, and show them as errors.

  static final int SIGNIFICAND_BITS = 52;

  static final int EXPONENT_BIAS = 1023;

  /** The implicit 1 bit that is omitted in significands of normal doubles. */
  static final long IMPLICIT_BIT = SIGNIFICAND_MASK + 1;

  static long getSignificand(double d) {
    checkArgument(isFinite(d), "not a normal value");
    int exponent = getExponent(d);
    long bits = doubleToRawLongBits(d);
    bits &= SIGNIFICAND_MASK;

                                    }
                                ),
                                "examples": {
                                    "normal": {
                                        "summary": "A normal example",
                                        "description": "A **normal** item works correctly.",
                                        "value": {
                                            "name": "Foo",

                                    }
                                ),
                                "examples": {
                                    "normal": {
                                        "summary": "A normal example",
                                        "description": "A **normal** item works correctly.",
                                        "value": {
                                            "name": "Foo",

                                    }
                                ),
                                "examples": {
                                    "normal": {
                                        "summary": "A normal example",
                                        "description": "A **normal** item works correctly.",
                                        "value": {
                                            "name": "Foo",

                                    }
                                ),
                                "examples": {
                                    "normal": {
                                        "summary": "A normal example",
                                        "description": "A **normal** item works correctly.",
                                        "value": {
                                            "name": "Foo",

## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.

This part is pretty normal, most of the code is probably already familiar to you:

## O aplicativo **FastAPI** normal

Vamos primeiro ver como o aplicativo da API normal se pareceria antes de adicionar o callback.

Ele terá uma *operação de rota* que receberá um corpo `Invoice`, e um parâmetro de consulta `callback_url` que conterá a URL para o callback.

Essa parte é bastante normal, a maior parte do código provavelmente já é familiar para você: