You feed your 80-page brand book into the agent and expect the output to sound like you. It doesn't. You blame the model, try another — same problem.
The problem isn't the model. The problem is that your brand book doesn't work as a prompt.
What separates an Identity file from a brand book
A brand book is written for humans: nice visuals, stories, some strategy. A human reads it once, internalises the atmosphere and then produces.
An agent can't do that. It reads from zero in every new session. It needs operational rules, not atmosphere.
An Identity file is:
- 1-3 pages of plain text. Markdown is good. PDF is bad.
- Voice rules, not adjectives. Not "bold, clear, direct" — but "no clichés. Use second person. Numbers before claims."
- Non-negotiables. What do you never say? Which tonalities are off-limits? Which word choices are fixed?
- Escalation rules. What does the agent do when unsure? Who does it message, in which channel?
The 30-minute method
You don't write the Identity file yourself. You let an AI extract it from you.
Step 1 (5 minutes): Open the AI chat tool of your choice. Say: "Help me write an Identity file for my brand. Ask me 15 questions about my voice, non-negotiables and output. I'll answer one at a time."
Step 2 (20 minutes): Answer the 15 questions. Be fast and concrete. If no answer comes, skip. You'll see: what makes you as a brand can almost always be said in one sentence per question.
Step 3 (5 minutes): Say: "Write that into an Identity file for me. Format: Markdown, max 3 pages. No adjectives — only operational rules another AI agent can use as a prompt."
You get a draft. Read it, edit two or three spots, done.
The litmus test
An Identity file is good when three things hold:
- A new team member could write on-brand from it alone. If not — operational rules are missing, too many adjectives in there.
- It was updated in the last 6 months. Identity isn't a rock, it shifts. Add a version number.
- You can paste it as the first block in any agent prompt. If it's too long (>3 pages), trim. Brevity is part of the voice.
What's next
Identity is axis 01 of 5. If you want to know where the rest of your stack stands, take the assessment. If you want the full blueprint — Identity is layer 01 in the Agentic OS Playbook.