Stop Over-Prompting: OpenAI’s New GPT-5.6 Guidelines Change Everything

OpenAI's new prompting guide for GPT-5.6 Sol advises leaner system prompts, improving eval scores by 10–15% and cutting tokens by 41–66% and costs by 33–67% in internal tests. The guide introduces a Programmatic Tool Calling section and a text.verbosity parameter, replacing prior XML and step-by-step instructions.