Hydroxycinnamoyl transferase that catalyzes the transfer of an acyl from p-coumaryol-CoA to agmatine, to produce coumaroyl agmatine. Can use feruloyl-CoA, caffeoyl-CoA and sinapoyl-CoA as acyl donors (PubMed:24908251, PubMed:27015846, PubMed:27354554). Seems to be able to transfer the acyl group from p-coumaroyl-CoA and feruloyl-CoA to the acyl acceptors putrescine and spermidine (PubMed:24908251). Highly expressed in roots. Expressed at low levels in flowers. Belongs to the plant acyltransferase family.