trigger trouble -- procedure not found

I'm having trouble creating a trigger. First i'm creating a function,
add_to_search in PL/pgSQL.

\df verifies the existance of this function:
smallint | add_to_search | text, text, text, integer

but when I call:

CREATE TRIGGER item_insert_search_add AFTER INSERT
ON item FOR EACH ROW
EXECUTE PROCEDURE add_to_search (name, description, reason, node_id);

I get:
ERROR: CreateTrigger: function add_to_search() does not exist

What am I missing here? It seems to me that I'm missing something very
simple, but I can't figure out what it is for the life of me.

Kevin Way