機宜文字官是宋代各路帥臣辟舉之軍事幕僚，主要設置於沿邊各路之軍事要地，尤其是宋夏衝突之後的陝西地區。機宜由安撫使等帥臣自行辟舉，所辟舉之人或爲親屬子弟或爲故舊部屬。機宜所負責之職務是以軍事機密事務爲主，諸如書寫奏章、入呈邊事、參與軍事謀畫、帶軍作戰等。對於實行「以文御武」之策略，以文臣領軍作戰的宋代，機宜以其久歷邊事，熟悉軍情之背景，充分發揮協助文臣領軍作戰之功能。

Policy guidance civil officials were Sung Dynasty military affairs personnel selected by commanders and officials and employed in the empire's military circuits. They were primarily assigned to strategic regions along military circuit borders, particularly along the Shaanxi region after the conflict between the Sung and the Xia. Autonomously selected by pacification officers and other high level military personnel, candidates were drawn from either family members or veteran subordinates. The professional responsibilities of policy guidance officials were primarily classified military affairs such as writing memorials to the throne, managing border affairs, participating in military planning, and leading troops in battle. As to the strategy of employing literati to achieve martial objectives, the Sung Dynasty, which habitually employed highly-educated officials to lead military personnel into battle, found policy guidance civil officials successfully fulfilling their appointed role of employing their lengthy experience in and knowledge of border affairs, plus long familiarity with the military ethos, to assist officials in waging martial campaigns.