functions are returns columns

Hi all.
I want that a function return a table rows (like the doc says at 33.4.4.
SQL Functions as Table Sources), but I want the a function return only a
few cols, so the same that I select into the func.
Modifying the doc example:

CREATE TABLE foo (fooid int, foosubid int, fooname text);
INSERT INTO foo VALUES (1, 1, 'Joe');
INSERT INTO foo VALUES (1, 2, 'Ed');
INSERT INTO foo VALUES (2, 1, 'Mary');

CREATE FUNCTION getfoo(int) RETURNS foo AS $$
SELECT fooid, foosubid FROM foo WHERE fooid = $1;
$$ LANGUAGE SQL;

This give me an error:

ERROR: return type mismatch in function declared to return foo
DETAIL: Final SELECT returns too few columns.
CONTEXT: SQL function "getfoo"

So, how do it?

Thanks,
Michele