"soFar","preFilters","cached","combinator","base","skip","checkNonElements","doneName","oldCache","newCache","elementMatcher","matchers","condense","newUnmatched","mapped","setMatcher","postFilter","postFinder","postSelector","temp","matcherOut","preMap","postMap","preexisting","contexts","multipleContexts","matcherIn","matcherFromTokens","checkContext","leadingRelative","implicitRelative","matchContext","matchAnyContext","elementMatchers","setMatchers","bySet","byElement","superMatcher","outerm...

"soFar","preFilters","cached","combinator","base","skip","checkNonElements","doneName","oldCache","newCache","elementMatcher","matchers","condense","newUnmatched","mapped","setMatcher","postFilter","postFinder","postSelector","temp","matcherOut","preMap","postMap","preexisting","contexts","multipleContexts","matcherIn","matcherFromTokens","checkContext","leadingRelative","implicitRelative","matchContext","matchAnyContext","elementMatchers","setMatchers","bySet","byElement","superMatcher","outerm...

///

/// info

To declare cookies, you need to use `Cookie`, because otherwise the parameters would be interpreted as query parameters.

///

## Recap { #recap }

This is not a limitation of **FastAPI**, it's part of the HTTP protocol.

///

## Recap { #recap }

```
X-Token: foo
X-Token: bar
```

The response would be like:

```JSON
{
    "X-Token values": [
        "bar",
        "foo"
    ]
}
```

## Recap { #recap }

Declare headers with `Header`, using the same common pattern as `Query`, `Path` and `Cookie`.

This is not a limitation of **FastAPI**, it's part of the HTTP protocol.

///

## Recap { #recap }

As these keys may not necessarily be part of the OpenAPI specification, some OpenAPI tools, for example [the OpenAPI validator](https://validator.swagger.io/), may not work with your generated schema.

///

## Recap { #recap }

You can use Pydantic's `Field` to declare extra validations and metadata for model attributes.

        "tax": 3.2
    }
}
```

instead of:

```JSON
{
    "name": "Foo",
    "description": "The pretender",
    "price": 42.0,
    "tax": 3.2
}
```

## Recap { #recap }

You can add multiple body parameters to your *path operation function*, even though a request can only have a single body.

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 { #recap-step-by-step }

### Step 1: import `FastAPI` { #step-1-import-fastapi }

{* ../../docs_src/first_steps/tutorial001.py hl[1] *}

///

```Python hl_lines="1"
async def needy_dependency(fresh_value: str = Depends(get_value, use_cache=False)):
    return {"fresh_value": fresh_value}
```

////

## Recap { #recap }

Apart from all the fancy words used here, the **Dependency Injection** system is quite simple.

Just functions that look the same as the *path operation functions*.