[4] Anthony was made vice-chancellor of the royal court around March 1298, replacing Gregory Bicskei, who was elected Archbishop of Esztergom a month before.
Along with the majority of prelates, Anthony was a strong confidant of Andrew III, whose legitimacy was disputed by the Capetian House of Anjou.
[5] Anthony performed a diplomatic mission to Brno (Brünn) in May 1299, where, as representative of the Hungarian king, he participated in the meeting between Wenceslaus II of Bohemia and Leo I of Galicia.
The conflict emerged between the politically isolated Bicskei and the rest of the Hungarian prelates – led by Archbishop John Hont-Pázmány – in the upcoming years.
[8] There, he acted as a judge in the lawsuit between Benedict Rád, Bishop of Veszprém and the abbot of the Bélakút Abbey over the right of collection of tithes of St. Gerard church in Kelenföld.
[12] Historian Sarolta Homonnai argued it was not in the pope's interest to appoint a strictly pro-royal prelate to the position of archbishop of Esztergom.
Anthony supported the claim of the young Wenceslaus to the Hungarian throne, along with overwhelming majority of the prelates led by John Hont-Pázmány.
[14][15] Anthony was a participant of the national synod convoked by papal legate Niccolò Boccasini (future Pope Benedict XI) in October 1301.
He also testified in the trial regarding the election of provost of Szepes Chapter (today Spišská Kapitula, Slovakia) before the court of papal legate Niccolò Boccasini in January 1302.
[18] Pope Boniface VIII declared Charles of Anjou the lawful king of Hungary on 31 May 1303, stating that Wenceslaus' election had been invalid.
By that time, majority of the prelates had already switched to the side of Charles one after another, but Anthony and Benedict Rád remained partisans of Wenceslaus, despite that the papal bull threatened his subjects with excommunication.
Wenceslaus who had succeeded his father in Bohemia renounced his claim to Hungary in favor of Otto III, Duke of Bavaria on 9 October 1305.