It's a good idea to experiment, but bad idea to just make up functions u take a risk of locking up your farm...the right function is this....
You will get a key in response something like this one....
signedCall("WanderingAnimalService.onBuyWanderingMustang", this.m_rewardId, this.m_buyReward);
This is a non repeatable service
you can produce one link per 24 hours with this
With that being said, now here is the Trick.......
1. Open farm> Charles BP ON> open market, Charles pop-up > Edit request> AMF> change UserService.publishUserAction> WanderingAnimalService.onCreateMustangReward
>Execute> Edit response> Amf> Data> rewardId and see key, copy key / Ctrl+c/.. / example my key 4dt53spa6gow0sk0sgsw8soc4 ... only work 1 key-1 day/
http://apps.facebook.com/onthefarm/reward.php?frHost= paste your id here &frId= paste your key here &frType=WanderingMustangFriendReward
Publish link in your wall... next time 5 friends click in your link and finish help to mustang...open farm, giftbox, place mustang and share mustang foal for your friends..