Place the carrots and red cabbage in a large bowl. Mix together the lime juice and agave syrup, and stir into the vegetables. Toss to mix well, and set aside.
Heat the oil in a small frying pan over a medium heat. Add the chilli and mustard seeds, and stir-fry for 20–30 seconds until fragrant and the mustard seeds start to 'pop'.
Scrape the contents of the frying pan over the salad, season well and toss to combine. Serve immediately.