Prompting Guide

GPT-5.5 works best when prompts define the outcome and leave room for the model to choose an efficient solution path. Compared with earlier models, you can often use shorter, more outcome-oriented prompts: describe what good looks like, what constraints matter, what evidence is available, and what the final answer should contain.

Avoid carrying over every instruction from an older prompt stack. Legacy prompts often over-specify the process because earlier models needed more help staying on track. With GPT-5.5, that can add noise, narrow the model's search space, or lead to overly mechanical answers.

For more detail on GPT-5.5 behavior changes, start with the [Using GPT-5.5 guide](/api/docs/guides/latest-model). This guide focuses on prompt changes that follow from those behavior changes.

The patterns here are starting points. Adapt them to your product surface, tools, evals, and user experience goals.

## Personality and behavior

GPT-5.5's default style is efficient, direct, and task-oriented. This is useful for production systems: responses stay focused, behavior is easier to steer, and the model avoids unnecessary conversational padding.

For customer-facing assistants, support workflows, coaching experiences, and other conversational products, define both personality and collaboration style.

- **Personality** controls how the assistant sounds: tone, warmth, directness, formality, humor, empathy, and level of polish.
- **Collaboration style** controls how the assistant works: when it asks questions, when it makes assumptions, how proactive it should be, how much context it gives, when it checks work, and how it handles uncertainty or risk.

Keep both short. Personality instructions should shape the user experience. Collaboration instructions should shape task behavior. Neither should replace clear goals, success criteria, tool rules, or stopping conditions.

Example personality block for a steady task-focused assistant: