HTTP 415 Unsupported Media Type means the server refuses to accept the request because the Content-Type of the request body is not supported. For example, sending XML to an endpoint that only accepts JSON.
The request specifies a Content-Type the server does not support for this endpoint.
The request body does not have a Content-Type header and the server cannot determine the format.
Check the API documentation for the expected Content-Type and set it in your request.
curl -X POST -H 'Content-Type: application/json' -d '{"key":"value"}' https://api.example.com/The API documentation should list which content types are accepted for each endpoint.