FastAPI - Add description for path parameter in swagger

Question

Imagine there is an app like that:

from fastapi import FastAPI

app = FastAPI()


@app.get("/items/{item_id}")
async def read_item(item_id: int):
    return {"item_id": item_id}

How could one add description for path parameter item_id in swagger?

Answer 1

You can add description for a specific parameter by using the description argument to the parameter type object:

item_id: int = Path(..., description="An id representing an item")

The ... represents the default value and should be included*.

Edit*: The current version of FastAPI throws an error if ... is included for Path objects, so leave it out if you're using a recent (2023) version.

Answer 2

Like this

@app.get("/items/{item_id}")
async def read_item(item_id: int):
    """
    item_id: Your item ID description will be here
    """
    return {"item_id": item_id}
    

swagger doc