How to Write a Great agents.md

This GitHub Blog article analyzes best practices for creating `agents.md` files—configuration files that define custom AI agents for GitHub Copilot—based on patterns from over 2,500 repositories. The focus is on building effective specialized AI assistants with specific personas and clear operational guidelines rather than generic helpers.

Key insights include: successful agents require specific personas ("test engineer," not "helpful assistant"), executable commands, and concrete code examples. The most effective configurations include explicit constraints—what agents should never touch (secrets, vendor directories, production configs). The article identifies six core components for winning agents: commands, testing practices, project structure, code style, git workflows, and safety boundaries. It provides actionable templates and emphasizes iterative improvement over perfect upfront planning.