Jephthah and his Daughter

Some people see Jephthah as irresponsible for making an unthinking vow which implies he must sacrifice his daughter to God … and God looks on and does nothing. However, is such an interpretation correct?

If Jephthah sacrificed his daughter to the Lord what he did was both contrary to the Law of Moses and an abomination in the eyes of the Lord. So … what did the vow actually mean and what did Jephthah actually do?