If you wish to check what Grapevine parses from your game's MSSP data, you can use this checker.
Grapevine follows the guidelines set on the TinTin++ MSSP docs page.
In order for this check to work, your game must send the
IAC WILL MSSP telnet option or respond to
mssp-request at the login prompt. Grapevine will send the term type
Grapevine if the game requests it.
If your game does not send
IAC WILL MSSP, Grapevine will send
mssp-request\n after 10 seconds. Grapevine will wait 20 seconds before giving up.