How to send a json string from android in java to realm app services and then insert document?

Hello everyone,

I have created a json object using JSONObject class in Java from Android Studio.
Then, I cast it to a string using toString() method.
I send that string in my mongodb function i have on Realm App Service as an argument using List<String> args = Arrays.asList(jsonObjectString); from java.
When I go to my function on Realm App Services, I can read and get back that string returning it using return arg and see my original string in my android application project.

Now the problem is when I want to use that argument to insert a new document in my Atlas collection.
I use on Realm App Services the method arg_json = JSON.parse(arg) to transform my string to an json object that I want to put as input to collection.insertOne(arg_json) but nothing happened.