From Ceremonial of Bishops (ISBN 0814618189 ):
"Master of Ceremonies
34 For a liturgical celebration, especially a celebration presided over by the bishop, to be distinguished by grace, simplicity, and order, a master of ceremonies is needed to prepare and direct the celebration in close cooperation with the bishop and others responsible for planning its several parts, and especially from a pastoral standpoint.
The master of ceremonies should be well-versed in the history and nature of the liturgy and in its laws and precepts. But equally he should be well-versed in pastoral science, so that he knows how to plan liturgical celebrations in a way that encourages fruitful participation by the people and enhances the beauty of the rites.
He should seek to ensure an observance of liturgical laws that is in accord with the true spirit of such laws and with those legitimate traditions of the particular Church that have pastoral value.
35 In due time he should arrange with the cantors, assistants, ministers, and celebrants the actions to be carried out and the texts to be used, but during the celebration he should exercise the greatest discretion: he is not to speak more than is necessary, nor replace the deacons or assistants at the side of the celebrant. The master of ceremonies should carry out his responsibilities with reverence, patience, and careful attention.
36 The master of ceremonies wears either an alb or a cassock and surplice. Within a celebration a master of ceremonies who is an ordained deacon may wear a dalmatic and other diaconal vestments."
From the General Instruction of the Roman Missal:
“ 106. It is desirable, at least in cathedrals and in larger churches, to have some competent minister or master of ceremonies, to see to the appropriate arrangement of sacred actions and to their being carried out by the sacred ministers and lay faithful with decorum, order and devotion.”
[Excerpts from the English translations of The Roman Missal (c) 2010 International Commission on English in the Liturgy Corporation and Ceremonial of Bishops (c) 1989 International Commission on English in the Liturgy Corporation. All rights reserved.]