When Onmyoryo was first set up, as hogi's duties only consisted of seizen, chiso (something like the present 'Feng Shui'), astronomy, astrology, calendar-making, judging lucky and unlucky days and the clock, they exclusively worked to observe astronomy, to manage the calendar and clock and to make predictions on good and bad luck concerning events using logical analyses based on inyo gogyo, while never performing religious ceremonies or magic rituals like jingikan or monks, they played a key role in selecting lucky days when building or reconstruction work was required at the Imperial Court and performed divinations for lucky and unlucky properties/directions for relocating the capital.
陰陽寮成立当初の方技は、純粋に占筮、地相（現在で言う「風水」的なもの）、天体観測、占星術、暦の作成、吉日凶日の判断、漏刻のみを職掌としていたため、もっぱら天文観測・暦時の管理・事の吉凶を陰陽五行に基づく理論的な分析によって予言するだけであって、神祇官や僧侶のような宗教的な儀礼や呪術は全く行わなかったが、朝廷において営繕を行う際の吉日選定や、土地・方角などの吉凶を占うことで遷都の際などに重要な役割を果たした。