As i understand it, summon requires the presence of a token in the inventory of the summoned player. Unwilling reception of items has been an issue that's surfaced in darke a number of times, and there seems to be a simple solution. In a manner similar to one player allowing another player to follow, there could be a command implemented where one player would have to allow another player to give them items. Are you going to accept something from someone if you don't want it in your possession? Probably not. Simple syntax:

trade allow <name>

Toggles the ability of <name>d player to give items to the one entering the command.

Of course, the stealth-requiring act of slipping something small into another person's inventory could be, and probably should be, a guild ability, if it is determined that the ability to do so will serve a useful purpose within the game.