Many of you are likely using AI coding agents like Cursor or Claude Code these days, right? We've entered an era where keeping a well-structured agent guide file in your project root allows agents to understand your project style perfectly. A prime example is AGENTS.md, which was first proposed by OpenAI and is now managed as an official open standard by the Linux Foundation's Agentic AI Foundation (AAIF).

However, many people end up cluttering these files with endless rules and coding style guidelines, hoping to make the agent work more perfectly. Surprisingly, this can actually backfire.

According to a recent paper presented at ICLR 2026, as project context files become heavier and more complex, the agent's actual task success rate drops, while inference costs increase by about 20%. It seems that when rules are too dense, agents get distracted by unnecessary file exploration or meaningless tests, causing them to lose sight of the important solutions.

Ultimately, the key is to strike a smart balance by keeping only the "unique project-specific rules" and "essential build/test commands." Since today's models are already quite smart, there's no need to waste tokens by explaining obvious technical stack knowledge.

One more pro tip: while Cursor and Windsurf support AGENTS.md well, Claude Code still prioritizes reading CLAUDE.md. Instead of struggling to keep both files in sync, I recommend simply connecting them with a symbolic link as shown below!

# AGENTS.md와 CLAUDE.md 싱크 맞추기 (macOS/Linux)
ln -s AGENTS.md CLAUDE.md

Remember: the lightest and clearest context creates the smartest and most cost-effective AI agents.