no need, this: 

```
const char *json_string_value(const json_t *string)
Returns the associated value of string as a null terminated UTF-8 encoded string, or NULL if string is not a JSON string.
The retuned value is read-only and must not be modified or freed by the user. It is valid as long as string exists, i.e. as long as its reference count has not dropped to zero.
```

is what I was wondering about.