Most often JSON is used to represent an object, for example {"a": 0} in which case you need the braces.  However a simple value such as 0 or "some string" on its own is also valid json and in that case must not have the braces.
Most often JSON is used to represent an object, for example {"a": 0} in which case you need the braces.  However a simple value such as 0 or "some string" on its own is also valid json and in that case must not have the braces.