OpenAi's GPT5 Practical Guide

OpenAI's new GPT-5 model represents a major leap forward in AI, offering more power, speed, and adaptability. But to truly harness its capabilities, developers need to adopt new strategies. This practical guide outlines how to migrate, prompt, and scale applications with this new frontier model.

Migrate to the Responses API

The first and most critical step is to move workflows to the new Responses API. Unlike the older Completions API, the Responses API is built for GPT-5 and allows the model to persist its "chains of thought" across multiple turns and tool calls.

This new infrastructure is essential for unlocking the model's full intelligence. It leads to better performance, improved caching, lower costs, and less "glue code," allowing teams to ship features faster.

Optimize Your Prompting Strategy

Your old prompts won't work as expected. GPT-5 is highly steerable, which means prompt quality is more important than ever. The guide details a systematic process for optimizing prompts.

Download the Guide

A New Prompting Workflow

• Start with Evals: Run existing prompts to establish a baseline and see where outputs fail.
  
  
• Inspect Reasoning: Use the Responses API to watch how the model "thinks" and pinpoint where it needs more steering.
  
  
• Metaprompt and Simplify: Use GPT-5 to help improve its own prompts. You'll often find that GPT-5 requires less scaffolding, and shorter, clearer instructions perform better.
  
  
• Template and Document: Lock successful prompts into a reusable library to ensure consistency.

Steer Behavior with New Controls

GPT-5 introduces new parameters to fine-tune its behavior. Developers can now control reasoning_effort (from minimal to high) to manage how much the model thinks before answering. You can also adjust verbosity (low, medium, or high) to control the length of the output.

Troubleshoot and Scale

The guide also provides resources for troubleshooting common pitfalls like overthinking, latency, or tool overuse. By adopting the Responses API, mastering this new approach to prompting, and using the new steering controls, startups can build more consistent, predictable, and accurate applications with GPT-5.