Shay>Npgsql currently always sends a describe as part of statement execution (for server-prepared messages the describe is done only once, at preparation-time). Vladimir, are you doing things differently here?
The same thing is for pgjdbc. It does use describe to identify result row format.
However, "CALL my_proc()" works just fine with current git master for both simple and extended protocol.
The missing part is "invoke functions via CALL statement".