Implicit conversions

I'm working on a project where request and response messages are serialized before sending across the wire. We do this by calling an override of ToString(). So a line in the code might look like

    response = myProvider.ProcessMessage(myMessage.ToString());

If I try to type

    response = myProvider.ProcessMessage(myMessage);

I get a build error stating that it cannot implicitly convert type 'SomeCoolMessage' to 'string.' So, what if I want to implicitly convert between the two? In the SomeCoolMessage class I add a new operator

    public static implicit operator string(SomeCoolMessage m)
    {
        return m.ToString();
    }

Now I can write

    response = myProvider.ProcessMessage(myMessage);

and everything just works.