Cause
The body, or a nested object such as content, target, audience or context, is not a JSON object.
What to do
Send a JSON object with the fields of the contract.
application/problem+json
{
"type": "https://masnet.com/developers/errors/invalid_shape",
"title": "Invalid body shape",
"status": 400,
"detail": "...",
"code": "invalid_shape",
"correlation_id": "..."
}