My statement is not fully correct. An agents.md file does reliably increase the cost for inference by 20% on average.
Researchers at ETH Zurich show that "Agents.md" files don't do much. "AI" is cosplay all the way down.
(Original title: Your AGENTS.md file doesn’t actually do anything)
https://pivot-to-ai.com/2026/08/27/your-agents-md-file-doesnt-actually-do-anything/