Methods & parameters¶

A JSON-RPC method is a regular Python function decorated with @entrypoint.method(). Parameters are declared using the same FastAPI building blocks you already know — Body, Header, Cookie, Depends, and Pydantic models.

import fastapi_jsonrpc as jsonrpc
from fastapi import Body
from pydantic import BaseModel

app = jsonrpc.API()
api_v1 = jsonrpc.Entrypoint('/api/v1/jsonrpc')


class Greeting(BaseModel):
    text: str
    language: str = 'en'


@api_v1.method()
def greet(
    name: str = Body(..., examples=['Ada']),
    loud: bool = Body(False),
) -> Greeting:
    text = f'Hello, {name}!'
    return Greeting(text=text.upper() if loud else text)


app.bind_entrypoint(api_v1)

Declaring parameters¶

FastAPI primitive	Ends up as
`Body(...)`	A field inside JSON-RPC `params`
`Header(...)`	An HTTP header on the enclosing POST request
`Cookie(...)`	A cookie on the enclosing POST request
Pydantic model	A nested object inside `params`
`Depends(...)`	Reused via FastAPI's DI — see Dependencies

Return types must be JSON-serialisable. Pydantic models are rendered into the OpenAPI/OpenRPC schemas automatically.

Async methods¶

async def methods are supported transparently:

@api_v1.method()
async def fetch_user(user_id: int = Body(...)) -> dict:
    return await users_repo.get(user_id)

Batching and notifications¶

JSON-RPC 2.0 batches and notifications (requests without id) are handled automatically. Each request in a batch gets its own dependency resolution — see Dependencies for per-batch vs per-request behaviour.

Multiple entrypoints¶

You can mount several entrypoints on the same API:

api_v1 = jsonrpc.Entrypoint('/api/v1/jsonrpc')
api_v2 = jsonrpc.Entrypoint('/api/v2/jsonrpc')

app.bind_entrypoint(api_v1)
app.bind_entrypoint(api_v2)

Each entrypoint has its own set of default errors, middlewares and dependencies.