Wolfram Research, Inc.
int MLPutFunction(MLINK link, char *s, long n) puts a function with head given by a symbol with name s and with n arguments to the MathLink connection specified by link.
After the call to MLPutFunction() other MathLink functions must be called to send the arguments of the function.
See The Mathematica Book: Section 2.12.4.
See also: MLPutString.