How to send messages to Firefox through devtools protocol?

i'm trying to write my own custom webdriver interface to control firefox through chrome devtools protocol (cdp). i launch firefox using firefox-esr --remote-debugging-port 0 and then it creates a websocket that i connect to using python:

async def main_client():
    async with websockets.connect("ws://localhost:34805/devtools/browser/f67014fd-9397-478d-a11e-66c189704ab0") as client_connection:
        while True:
            message = input("type in a command: ")
            await client_connection.send(message)

asyncio.run(main_client())

then i send a message in json format

{
"command":"Runtime.evaluate",
"parameters":{"expression": "console.log(\"this is a message\")"}
}

the problem is that when i send the message nothing happens on the receiving end. does anyone know how to send messages over websocket to firefox?

thanks