Research from five 2026 studies on AGENTS.md context files for coding agents shows mixed results: hand-written files provide modest benefits (around 2-4 percentage points) for specifying non-standard practices, while generated files slightly hurt performance, with all approaches increasing inference costs by roughly 20 percent. File structure and organization matter less than which rules are presented and when, and context files outperform skills only for knowledge models lack and need on most tasks.