Don't write the identity file from scratch yourself because you will hate it and quit; instead, open an AI tool and have it interview you by asking 15 questions about how you work, what you want, what you don't want, what frustrates you about AI, and what rules you want enforced, then have the AI draft it, you edit it, and ship a first version that is about 70% right, which you can refine over the next 3 weeks.