OpenAI · AGENTS.md and prompt instructions
Best Codexrules & configs — RuleSell
Codex is OpenAI's terminal-based coding agent (the open-source companion CLI). Project guidance lives in AGENTS.md at the repo root — a markdown file the agent reads on session start.
Top 5 Codex rules right now
Ranked by quality score — freshness, schema completeness, and review signals. Refreshed daily.
No Codexlistings yet during beta — but they're landing fast. Be the first to publish for Codex:
Why use Codex rules from RuleSell
- AGENTS.md templates for popular stacks — Next.js, Rails, Django, Go, Rust.
- Compatible with the AGENTS.md spec used by other agentic CLIs.
- Quality-scored and version-pinned.
- Copy-paste install at repo root.
How to use Codex rules
1. Pick a Codex rule
Browse the listings below and open one that matches your stack.
2. Copy the file contents
Click "Copy" on the listing — or download the raw file from the source URL.
3. Paste into AGENTS.md at repo root
Drop the rule into AGENTS.md at repo root. The exact command: cp rule.AGENTS.md ./AGENTS.md
4. Restart Codex
Restart your Codex session so the new rule is loaded. Verify it appears in the active context.
cp rule.AGENTS.md ./AGENTS.mdCodex rules — frequently asked
What is AGENTS.md?
AGENTS.md is a markdown file at the repo root that agentic coding tools (Codex, others adopting the convention) read on session start. It describes your project's conventions, commands, and gotchas so the agent doesn't have to re-discover them.
Is Codex CLI the same as ChatGPT Codex?
No. The Codex CLI is OpenAI's open-source terminal agent. ChatGPT Codex is the cloud-hosted product inside ChatGPT. They share a name and roots but are different products.
Does Codex support custom MCP servers?
Codex's MCP support varies by version — check the upstream README. RuleSell tags MCP servers with the environments they're tested in.
Can I use the same AGENTS.md across Claude Code and Codex?
Often yes — AGENTS.md is a portable convention. Claude Code reads it as project context too. You can also link your CLAUDE.md and AGENTS.md to each other.
Is the Codex CLI free?
The CLI is open source. Model usage is billed by OpenAI at your API rate.