ADK does not support Python 3.10+ union type syntax (`str | None`)

[ecanlar]

[sasha-gitg]

Please provide more detail in the body of the issue and not an attachment.

[jomalsan]

I'll chime in here as I have seen similar behaviour, although I don't have a full repro ready.

When using a custom function as a tool, that function must use the Optional[str] notation for its parameter types if using FunctionTool to wrap it. If you use str | None then the framework will throw.

# works when wrapped with FunctionTool
def greet(name: Optional[str]) -> str:
    return f"Hello {name}"

# raises an exception when the framework maps model output to the input types
def greet(name: str | None) -> str:
    return f"Hello {name}"