Path Operation Configuration

🎯 What You'll Learn

• Configure response status codes using status constants
• Organize endpoints with tags and metadata
• Add descriptions using docstrings and parameters
• Mark endpoints as deprecated

📚 Theory

There are several parameters that you can pass to your path operation decorator to configure it.

⚠️ Important: Notice that these parameters are passed directly to the path operation decorator, not to your path operation function.

Response Status Code

You can define the (HTTP) status_code to be used in the response of your path operation.

You can pass directly the int code, like 404.

But if you don't remember what each number code is for, you can use the shortcut constants in status:

from fastapi import FastAPI, status
from pydantic import BaseModel

app = FastAPI()

class Item(BaseModel):
    name: str
    description: str | None = None
    price: float
    tax: float | None = None
    tags: set[str] = set()

@app.post("/items/", response_model=Item, status_code=status.HTTP_201_CREATED)
async def create_item(item: Item):
    return item

That status code will be used in the response and will be added to the OpenAPI schema.

Tags

You can add tags to your path operation, pass the parameter tags with a list of str (commonly just one str):

@app.get("/items/", tags=["items"])
async def read_items():
    return [{"name": "Foo", "price": 42}]

@app.get("/users/", tags=["users"])
async def read_users():
    return [{"username": "johndoe"}]

They will be added to the OpenAPI schema and used by the automatic documentation interfaces.

Tags with Enums

If you have a big application, you might end up accumulating several tags, and you would want to make sure you always use the same tag for related path operations.

In these cases, it could make sense to store the tags in an Enum.

FastAPI supports that the same way as with plain strings:

from enum import Enum

class Tags(Enum):
    items = "items"
    users = "users"

@app.get("/elements/", tags=[Tags.items])
async def read_elements():
    return ["Portal gun", "Plumbus"]

Summary and description

You can add a summary and description:

@app.post(
    "/items/",
    response_model=Item,
    summary="Create an item",
    description="Create an item with all the information, name, description, price, tax and a set of unique tags",
)
async def create_item(item: Item):
    return item

Description from docstring

As descriptions tend to be long and cover multiple lines, you can declare the path operation description in the function docstring and FastAPI will read it from there.

You can write Markdown in the docstring, it will be interpreted and displayed correctly (taking into account docstring indentation).

@app.post("/items/", response_model=Item, summary="Create an item")
async def create_item(item: Item):
    """
    Create an item with all the information:

    - **name**: each item must have a name
    - **description**: a long description
    - **price**: required
    - **tax**: if the item doesn't have tax, you can omit this
    - **tags**: a set of unique tag strings for this item
    """
    return item

Deprecate a path operation

If you need to mark a path operation as deprecated, but without removing it, pass the parameter deprecated:

@app.get("/elements/", tags=["items"], deprecated=True)
async def read_elements():
    return [{"item_id": "Foo"}]

It will be clearly marked as deprecated in the interactive docs.

🔧 Key Concepts

• Status Constants: Use status.HTTP_201_CREATED instead of 201
• Tags: Organize endpoints into logical groups
• Docstrings: Multi-line descriptions with Markdown support
• Deprecation: Mark endpoints as obsolete without removing them

📝 Recap

You can configure and add metadata for your path operations easily by passing parameters to the path operation decorators.

💡 Best Practices

• Always use status constants for better code readability
• Group related endpoints with consistent tags
• Use docstrings for complex endpoint descriptions
• Mark deprecated endpoints instead of immediately removing them
• Keep response descriptions specific and helpful

🔗 Additional Resources

• FastAPI Path Operation Configuration
• HTTP Status Codes