I've heard that model agents like a large jawbone: is there a way to increase my jaw?

Jaw: Yes. By having genioplasty or orthognathic surgery. But the dimensions should be in harmony with rest of the face.

Larger Jaw: There are several ways to increase the dimensions of your mandible (lower jaw). Perhaps the easiest and least invasive method is by inserting custom-designed implants under the soft tissue in the areas you want to bulk up. This is a relatively simple procedure, usually with little down time.