Codex Prompt Engineering

Knowledge snapshot: 2026-02-20

Purpose

Use this skill to design or review prompts for Codex/GPT coding agents with focus on:

• quality and reliability
• token efficiency
• correct tool usage
• safe autonomy

Use When

• Writing or revising system prompts for coding agents
• Debugging weak agent behavior (stalling, verbosity, bad tool calls)
• Calibrating reasoning_effort (none|low|medium|high|xhigh)
• Defining tool orchestration and planning behaviors
• Building evaluation loops for prompt iteration