pydantic を使う

pip install "squarecloud[pydantic]"

import squarecloud as square
from squarecloud import Endpoint
from pydantic import BaseModel

class Animal(BaseModel):
    name: str
    age: int

@client.on_request(Endpoint.status())
async def get_extra_param(before, after, extra: Animal):
    print(extra.name)
    print(extra.age)

async def main():
    client = square.Client('your api key')
    await client.app_status('application_id', extra={'name': 'felix', 'age': 3})