Petty Magic, Tricks of the trade Options

[Aerospider]

Something's always bugged me a little about how SR never made provision for weak and/or trivial magic. I prefer the notion that magicians, in their studying, play around with their mana-crafting abilities and learn little tricks that, whilst potentially entertaining, don't have the scope to achieve anything significant, as opposed to the idea that they just learn a dozen powerful spells and live mundane lives between runs.

So I came up with this positive quality (restricted to magicians and mystic adepts).
Let me know what you think in terms of balance and play – this is pretty much first draft.

Petty Magic: 10 BP

The magician can perform little tricks and sleights to entertain, confuse, or just pass the time. If the player can give the GM a reasonable explanation of how this mini-sorcery might aid him in a task (e.g. winning over a suspicious NPC by showing him some nifty but minor illusion or aiding a palming attempt with some mana-fueled misdirection) he may make a Spellcasting + Magic (2) roll. Every net hit adds one die to his main skill check, whilst failure to meet the threshold will incur a -2 distraction penalty. There is no drain for this but it does extend the time the main task takes by a complex action. No focus or spirit aid may assist with the Petty Magic roll.

Too strong?
Too unnecessary?