OpenAI Releases Detailed Prompt Guide for GPT-4o

OpenAI has released a detailed prompt guide for developers targeting "GPT-4o" (development codename: Astra). The guide encompasses methods for instructing the model to take more proactive actions, a banned word list to avoid AI-specific boilerplate expressions, and tips to suppress excessive code testing.

As generative AI becomes widely used, AI-specific stereotypical expressions such as "will transform the domain" and "of course!"—the so-called "slop"—have become a source of discomfort for many users. Such expressions not only diminish the quality of AI-generated content but have also been pointed out as factors that erode reader and user trust. OpenAI's decision to directly address this issue in an official guide reflects a growing industry-wide interest in "output quality."

The guide presents concrete prompt design strategies for encouraging the model to adopt a "more proactive stance." For example, it explains methods for prompting the model not merely to wait for user instructions but to proactively suggest next steps when appropriate. Additionally, it includes mitigation techniques for the problem of models adding excessive test code when developers request code generation.

The provision of a banned word list has particularly high practical value. Until now, developers have had to either implement custom filtering to remove boilerplate expressions from AI outputs or adjust prompts through trial and error. By officially specifying "expressions to avoid," this guidance helps reduce such overhead.

OpenAI's systematic compilation and public release of a detailed prompt guide demonstrates that "optimizing how to use the model" is becoming as important as improving model performance itself. Regardless of how capable a model is, output quality varies significantly depending on how instructions are framed. From this perspective, prompt design is transitioning from the concern of a few power users to foundational knowledge that developers across the board should master.

Going forward, attention will focus on how thoroughly this official guide penetrates the developer community and improves output quality in actual applications. It will also be important to observe how the specific contents of the banned word list and concrete techniques for preventing code testing excess are applied in practice.