You can tell it to do so, but what you'll find is it knows to do it when it needs to. This is another case of "don't overthink it". Just let your agent decide when spinning up sub-agents makes sense.

If you focus too much on optimization, and you do so in the wrong ways, you'll actually find you saved no time/money/tokens vs just letting it decide when to do it. This applies as much to Agentic engineering as it did with programming pre-AI.

tl;dr it will literally do it for you, and it'll tell you when it does so