To my surprise, if you write cirq.X**"text" instead of cirq.X**sympy.Symbol("text"), thing mostly work. For example, you can run a sweep over the circuit with a dictionary mapping "text" to a value and you'll get samples back. This is because cirq.resolve_parameters treats strings as a shorthand for sympy.Symbol, as a way of removing boilerplate when specifying sweeps.

However, cirq.is_parameterized often does not recognize gates with string parameters as being parameterized. For example it fails on the case I gave above.

I think treating strings as implicitly being symbols is a reasonable idea, and I propose we codify this. Fixing it would involve finding all places with isinstance sympy.Basic checks and replacing them with is_parameterized calls, and then is_parameterized would also handle the string case.