This is no longer a part of the World of Warcraft API. Crafting API was absorbed into Tradeskill API. It was removed in patch 3.0.

CatalystName, 1 GetCraftSpellFocus(index)

Arguments

index 

Numeric - 1 to GetNumCrafts()

Returns

When called while the enchanting screen is open, this function returns which rod is required, if any. I don't know whether this function also applies to other types of crafts or spells.

Returns two values when a rod is required: a string that contains the name of the rod, and the number "1". I don't know what the "1" means.

Returns nil if no rods are required.