The attribute [DataType]
may not be used on Output parameters.
Instead it is defined on the method if they are [User]
methods or [Function]
methods inside a class with [FunctionContainer]
attribute.
If the method is the [Execution] __Process
method the [DataType]
attribute is positioned on the [Function]
class.
You can also use the provided automatic Code Fix to remove the attribute and put it in the correct place. ( Press Alt + Enter on the Error line to find the Code Fix in the context menu)
Move the attribute to the correct place.