The GPT-5.5 Decision Memo Prompt

A 12-minute prompt that turns ChatGPT's updated default model into a sharper decision partner.

GPT-5.5 Instant's June 24 update is best tested on the kind of decision that normally creates a messy Slack thread: vendor selection, hiring priority, budget tradeoff, product timing, or whether to pause a project.

The mistake is asking, "What should I do?" That invites soft advice. The better move is to frame the decision like a memo and force a recommendation.

Use this decision memo prompt

The Prompt

I need to make a business decision. Decision: [STATE DECISION] Context: [PASTE FACTS] Constraints: [BUDGET, TIME, PEOPLE, RISK, CUSTOMER IMPACT] Success criteria: [WHAT WINNING MEANS] Options I am considering: [OPTION A, OPTION B, OPTION C] Analyze the options in a table. Then identify hidden assumptions, second-order risks, and what information would change the recommendation. End with one forced recommendation, a 3-sentence rationale, and the first action to take in the next 24 hours.

Add this follow-up challenge

Argue against your recommendation. Name the strongest reason it could fail, the earliest warning sign, and the cheapest test that would reveal whether the recommendation is wrong.

Why this prompt works

• It makes constraints explicit.
• It asks for the information that would change the answer.
• It demands one recommendation and one immediate action.

That combination is what separates a decision memo from AI-flavored brainstorming.

Where this prompt helps most

• Vendor selection.
• Budget allocation.
• Hiring sequence.
• Product prioritization.
• Sales or marketing experiment choice.

ChatGPT may still invent missing context if you leave gaps. Use "TK" for unknowns. If a decision depends on current prices, legal duties, medical judgment, or financial advice, verify outside the chat before acting.

Source: OpenAI ChatGPT release notes