If you are getting an error when sending an Insert into statement via REST API like the one below
{"@type":"generic_error","error_code":40000,"message":"Statement type `io.confluent.ksql.parser.KsqlParser$PreparedStatement' not supported for this resource"}
The query example
INSERT INTO USER_GAME (USER, GAME) VALUES ('Test', STRUCT(SCORE:=80,LIVES:=0,LEVEL:=1));
make sure you are poinnting to the /ksql endpoint , and not the /query endpoint.
You can find more documentation ksqlDB Documentation - REST API