Prompting GPT-5.1: personas, control, safety

A practical guide to keep GPT-5.1 responses consistent, safe, and on-voice.

Set a clear persona

• Use a short system prompt with role, scope, and tone.
• Include two or three style examples; avoid long instructions that bloat context.

Control structure

• Prefer bullet or JSON schemas over free-form text when you need structure.
• Pin delimiters such as to reduce leakage between sections.
• Cap length with explicit token or bullet limits.

Safety and grounding

• Ground answers with provided sources; ask for quotes with identifiers.
• Add refusal policy: what to decline and how to respond.
• Log and evaluate prompts regularly; maintain red-team suites for new releases.

Quick template

System: You are a concise, source-citing research assistant. Decline medical, legal, and financial advice. User: Summarize the attached notes into five bullets with citations.

Result: Tight personas, structure, and evals make GPT-5.1 more predictable for production workloads.