We don’t ask the saint(s) to do anything for us in place of God, rather we simply ask them go to God with us for whatever intention we have.
Laudatur Iesus Christus.
We do, however, ask the Saints to do things for us in cooperation with God. Angles and Saints are both active in the service of God and His Kingdom. Many prayers to Saints (and Angels if one considers them separately) ask for direct assistance as well as prayers. The Saints are authorized to do this work for God, as a reward or their merits:
His master said to him, ‘Well done, my good and faithful servant. Since you were faithful in small matters, I will give you great responsibilities. Come, share your master’s joy.’ (Matthew (NAB) 25:21.)
Here is an example, purportedly written by Pope Leo XIII:
To thee, O blessed Joseph, do we come in our tribulation, and having implored the help of thy most holy Spouse, we confidently invoke thy patronage also. Through that charity which bound thee to the immaculate Virgin Mother of God and through the paternal love with which thou embraced the Child Jesus, we humbly beg thee to graciously regard the inheritance which Jesus Christ has purchased by his Blood, and with thy power and strength to aid us in our necessities.
O most watchful Guardian of the Holy Family, defend the chosen children of Jesus Christ; O most loving father, ward off from us every contagion of error and corrupting influence; O our most mighty protector, be propitious to us and from heaven assist us in our struggle with the power of darkness; and, as once thou rescued the Child Jesus from deadly peril, so now protect God’s Holy Church from the snares of the enemy and from all adversity; shield, too, each one of us by thy constant protection, so that, supported by thy example and thy aid, we may be able to live piously, to die holy, and to obtain eternal happiness in heaven. Amen.
(See,
preces-latinae.org/thesaurus/Ioseph/AdTe.html.)
This is also clear in the prayer to one’s guardian angel, as it appears in the present Handbook of Indulgencies:
Angel sent by God to guide me,
be my light and walk beside me;
Be my guardian and protect me;
On the baths of life direct me.
(Indulgenced Grant No. 8. See also,
preces-latinae.org/thesaurus/Basics/AngeleDei.html which says, in part: As best can be determined, this prayer is an 11th/12th century interpolation of a prayer composed by Reginald of Canterbury, who died sometime after 1109. This prayer is from Reginald’s Life of St. Malchus (d. c 390), a famous hermit who was a friend of St. Jerome (c 341-420).)
Hail holy Queen, Mother of mercy, hail, our life, our sweetness, and our hope. To you we cry, the children of Eve; to you we send up our sighs, mourning and weeping in this land of exile. Turn, then, most gracious advocate, your eyes of mercy toward us; lead us home at last and show us the blessed fruit of your womb, Jesus: O clement, O loving, O sweet Virgin Mary.
(Indulgenced Grant No. 51. See also,
preces-latinae.org/thesaurus/BVM/SalveRegina.html, which says, in part: Today this prayer is one of the final Marian Antiphons that conclude Compline in the Divine Office and it is also used in conjunction with the Rosary. A partial indulgence is granted to the faithful who devoutly recite this prayer.)
One should not forget that we have work to do, even in the rest of the Kingdom; it is life, not death into which we are reborn.
Spiritus Sapientiae nobiscum.
John Hiner