In GIRM 120-170, we covered the situation in which a deacon does not serve at Mass. Every deacon, and every priest or liturgist who serves with one, should be aware of the prescriptions of GIRM 171-186, which start here:
171. When he is present at the celebration of the Eucharist, a Deacon should exercise his ministry, wearing sacred vestments. In fact, the Deacon:
a) assists the Priest and walks at his side;
b) ministers at the altar, both as regards the chalice and the book;
c) proclaims the Gospel and may, at the direction of the Priest Celebrant, give the Homily (cf. no. 66);
d) guides the faithful people by giving appropriate instructions, and announces the intentions of the Universal Prayer;
e) assists the Priest Celebrant in distributing Communion, and purifies and arranges the sacred vessels;
f) carries out the duties of other ministers himself, if necessary, when none of them is present.
There is a virtue in a parish, if not a diocese, being fairly consistent on these functions. In my experience these six points have plusses and minuses in practice.
As a cleric, 171a and b seem quite appropriate, as is the prescription for liturgical involvement when present at Mass.
171c implies preparation. Even when not preaching, proclaiming the Gospel is a significant task that a person is hard-pressed to “wing” without preparation. As such, every deacon candidate should probably be an above-average lector.
171d is the prescription about which I have the most doubts. I think the need for a “commentator” is minimal in ordinary situations. And while there may be a historical pedigree for the deacon leading these prayers, it seems more appropriate to leave it to the laity. I will accommodate a deacon in this situation, but it might mean shunting aside someone who has prepared the announcing of these prayers. If the deacon is already proclaiming the Gospel, that would seem to be sufficient role.
171 e and f make practical sense.
Thoughts, especially from deacons out there?