Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add ching-kuo/claude-codex --skill codex-mcpgit clone --depth 1 https://github.com/ching-kuo/claude-codexWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/ching-kuo/claude-codex/codex-mcp)<a href="https://agentmods.dev/skills/ching-kuo/claude-codex/codex-mcp"><img src="https://agentmods.dev/badge/skills/ching-kuo/claude-codex/codex-mcp/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/ching-kuo/claude-codex/codex-mcp"><img src="https://agentmods.dev/badge/skills/ching-kuo/claude-codex/codex-mcp.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00043 | $0.00508 |
| Opus 5.5 | $0.00017 | $0.00203 |
| Sonnet 5.5 | $0.00009 | $0.00102 |
| Haiku 4.5 | $0.00004 | $0.00051 |
Grade A, and why
codex-mcp scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
Codex MCP Usage Guide
Tools
| Tool | Purpose |
|---|---|
mcp__codex__codex |
Start a new Codex session. Returns a threadId + response. |
mcp__codex__codex-reply |
Continue an existing session using threadId. |
Session Management
Codex sessions are stateful via threadId. Always:
- Save the
threadIdfrom the firstmcp__codex__codexcall - Use
mcp__codex__codex-replywith that threadId for all follow-ups - Never start a new session when continuing the same task — context carries forward
Key Parameters
sandbox
| Mode | When to Use |
|---|---|
read-only |
Plan review, code audit, Q&A — Codex reads but cannot write files |
workspace-write |
Implementation — Codex writes files in the project directory |
approval-policy
| Policy | When to Use |
|---|---|
never |
Review-only tasks where no shell commands are needed |
on-failure |
Implementation — auto-approve commands, intervene on errors |
developer-instructions
Inject a persona or constraints into Codex without polluting the main prompt.
Always include: "Be concise. Do not include your reasoning process in the response. Only output the result."
Prompting Best Practices
- Termination signals: Ask Codex to reply "APPROVED" or "CHANGES NEEDED" — gives clear loop control
- Feedback verbatim: When sending review feedback via codex-reply, quote specific issues exactly. Do not summarize.
- Concise responses: Always instruct Codex to be concise via developer-instructions to save tokens
- Max iterations: Always enforce a hard cap (default: 5) on review loops
stderr Suppression
The MCP server config uses 2>/dev/null at the process level.
Individual tool calls do NOT need stderr suppression — MCP returns structured JSON-RPC responses only.
See reference.md for detailed examples and patterns.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 53 lines · 43 tokens per session scan A d95235921943
codex-mcp is a skill published in the GitHub repository ching-kuo/claude-codex (24 stars, last pushed 6mo ago), licensed MIT. It adds 43 tokens to every session and 508 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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