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Example Code

from fastapi import FastAPI, Query
from pydantic import BaseModel, Field

app = FastAPI()


class PaginateParams(BaseModel):
    limit: int = Field(100, gt=0, le=100)
    offset: int = Field(0, ge=0)

class FilterParams(BaseModel):
    order_by: Literal['created_at', 'updated_at'] = 'created_at'
    tags: list[str] = []

@app.get('/items/')
async def read_items(paginator: PaginateParams, filter_query: FilterParams = Query()):

    return [paginator, filter_query]

Description

Currently, GET to this api with http://localhost:8000/items/?limit=10&offset=0&order_by=created_at&tags=pop&tags=metal will return with code 422.
Only one query parameter model is supported.

Sometimes this will cause too much definition of Parameter classes.
If multiple query parameter model allowed, some parameter classes can be reused and then reduce parameter classes definition.

Operating System

macOS

Operating System Details

No response

FastAPI Version

0.119.1

Pydantic Version

2.12.3

Python Version

3.13.9

Additional Context

No response