You're storing messages, how are you guaranteeing safety of those messages when it looks like one can seemingly just blast through your API calls to find messages when one isn't even on that server?
And a few extra additional seconds of research shows that they don't change the token unless you change your password, as opposed to having the token expire after every session.
The normal token system revokes on password change, if you want to revoke and have extra security we offer MFA login which has unique tokens per login. If security is of importance to you then use MFA.