how to create a composite type as return type for a Function as Table Source

Hello,

I want to make a Function as table source. As rettype you have to give a
composite type but how do I make those? I'm using an new empty table with
the the datatypes (INT, INT8, TEXT and a TIMESTAMP) I need.

Is this the normal way how to make composite types?

Example:

CREATE TABLE bigint_int_text_timestamp (
column_1 INT8,
column_2 INT,
column_3 TEXT,
column_4 TIMESTAMP);

CREATE OR REPLACE FUNCTION get_reservations (int) RETURNS SETOF
bigint_int_text AS $$

SELECT r.id,
p.id,
description,
last_time
FROM reservations r,
persons p
WHERE product_id = $1

$$ LANGUAGE SQL;