Perhaps you mean "prototype" ? ANSI C isn't object oriented and doesn't define the word "method" or phrase "method signature" because they are OO concepts. They are instead called "functions" and "prototypes" define the parameters that a function will receive.
Also, you shouldn't be writing code off of other people's examples. You should read the documentation so that you know how to handle every case that needs to be handled in your situation.
Anyway, callback functions (which is what you are asking about, right?) use the same key-value tuples that are defined throughout the rest of the mitai client library. Read the documentation and defined your callback to receive the necessary NULL-terminated args list.