k-o-i Greetings!
{"error": {"requestid": "c4f88e85-98f0-46e0-8ffa-xxxxxxxxxxxx", "code": 400, "message": "Invalid JSON in request body"}}
Based on the response from the API call, it seems that the JSON in the request body is invalid. Please check the JSON in the request body and make sure it is valid.
In the content of the API call you provided, there seems to be a syntax error in the JSON.
There is a comma after the last element in the "messages" array. Removing that comma should fix the issue.
Please try making the API call again with the corrected JSON and see if it resolves the issue.
I also see that your issue has been addressed on the Stack overflow
Do let us know if that helps or have any other queries.