Agent skill

Codex Explain

Explain complex code via Codex exec. An agent skill from sd0xdev/sd0x-harness.

MITAuto-check passedDevelopment

Install Codex Explain

skills CLI

$ npx skills add sd0xdev/sd0x-harness --skill codex-explain -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install sd0xdev/sd0x-harness codex-explain --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/sd0xdev/sd0x-harness.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/codex-explain .claude/skills/codex-explain && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "codex-explain" agent skill from https://github.com/sd0xdev/sd0x-harness/tree/main/skills/codex-explain into .claude/skills/codex-explain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "codex-explain", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/sd0xdev/sd0x-harness/tree/main/skills/codex-explain

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add sd0xdev/sd0x-harness --skill codex-explain -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install sd0xdev/sd0x-harness codex-explain --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/sd0xdev/sd0x-harness.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/codex-explain .agents/skills/codex-explain && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "codex-explain" agent skill from https://github.com/sd0xdev/sd0x-harness/tree/main/skills/codex-explain into .agents/skills/codex-explain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "codex-explain", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add sd0xdev/sd0x-harness --skill codex-explain -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install sd0xdev/sd0x-harness codex-explain --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/sd0xdev/sd0x-harness.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/codex-explain .cursor/skills/codex-explain && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "codex-explain" agent skill from https://github.com/sd0xdev/sd0x-harness/tree/main/skills/codex-explain into .cursor/skills/codex-explain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "codex-explain", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/sd0xdev/sd0x-harness.git --path skills/codex-explain

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add sd0xdev/sd0x-harness --skill codex-explain -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install sd0xdev/sd0x-harness codex-explain --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/sd0xdev/sd0x-harness.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/codex-explain .gemini/skills/codex-explain && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "codex-explain" agent skill from https://github.com/sd0xdev/sd0x-harness/tree/main/skills/codex-explain into .gemini/skills/codex-explain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "codex-explain", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install sd0xdev/sd0x-harness codex-explain

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add sd0xdev/sd0x-harness --skill codex-explain -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/sd0xdev/sd0x-harness.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/codex-explain .github/skills/codex-explain && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "codex-explain" agent skill from https://github.com/sd0xdev/sd0x-harness/tree/main/skills/codex-explain into .github/skills/codex-explain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "codex-explain", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add sd0xdev/sd0x-harness --skill codex-explain -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install sd0xdev/sd0x-harness codex-explain --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/sd0xdev/sd0x-harness.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/codex-explain .opencode/skills/codex-explain && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "codex-explain" agent skill from https://github.com/sd0xdev/sd0x-harness/tree/main/skills/codex-explain into .opencode/skills/codex-explain/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "codex-explain", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: codex-explain
GitHub stars: 192
Token cost: ~560 tokens
SKILL.md length: 111 words
Files: 2 (incl. references)
Skills in repo: 89
Repo updated: Oct 8, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Explain complex code via Codex exec. An agent skill from sd0xdev/sd0x-harness.

Works in 2 steps: Read Target File → Codex Explanation
: understanding complex logic
SKILL.md covers Trigger, When NOT to Use, Workflow and Depth Levels, plus 4 more sections
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Codex Explain is an agent skill from sd0xdev/sd0x-harness. Explain complex code via Codex exec. Use when: understanding complex logic, tracing data flow, onboarding to unfamiliar code. Not for: code review (use codex-code-review), exploration (use code-explore). Output: structured explanation at chosen depth.

Its SKILL.md is about 560 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/codex-prompt-explain.md`).

It sits in Development, covering Code review. The repository describes itself as: The harness layer for Claude Code — a reference implementation of harness engineering with hook-enforced dual review, state-machine gates that survive context compaction, and… The licence is MIT.

When your agent uses it

: understanding complex logic
Tracing data flow
Onboarding to unfamiliar code

Example prompts

“/codex-explain”

Requirements

Pre-approved tools (allowed-tools): Read, Grep, Glob, Bash(node:*), Write

Workflow steps

2 steps, taken from the step headings in SKILL.md.

Read Target File
Codex Explanation

What it can do on your machine

Read from SKILL.md and the folder at commit a4d4bc1. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves these tools, so the agent can use them without asking each time:
- Read
- Grep
- Glob
- Bash(node:*)
- Write
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md (its code samples are markdown).
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Codex Explain loads about 560 tokens when it runs, and up to ~1.2k if it reads all its reference files. Until then it costs about 66 tokens; SKILL.md has 111 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~66
When it runs · the whole SKILL.md, loaded when a task matches: ~560
With references · SKILL.md plus every file in references/, read only if the agent opens them: ~1.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from sd0xdev/sd0x-harness at commit a4d4bc1, republished under its MIT licence (© sd0xdev). 111 words, ~560 tokens.

Download SKILL.mdSave it as .claude/skills/codex-explain/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.

name: codex-explain
description: Explain complex code via Codex exec. Use when: understanding complex logic, tracing data flow, onboarding to unfamiliar code. Not for: code review (use codex-code-review), exploration (use code-explore). Output: structured explanation at chosen depth.
allowed-tools: Read, Grep, Glob, Bash(node:*), Write

Codex Explain Skill

Trigger

Keywords: explain code, what does this do, how does this work, code walkthrough

When NOT to Use

Code review (use codex-code-review)
Bug investigation (use bug-fix or issue-analyze)
Architecture overview (use code-explore)

Workflow

Read target → [Collect context] → Codex explain → Output explanation

Step 1: Read Target File

Read file content. If --lines specified, extract only that range.

Step 2: Codex Explanation

Dispatch per @skills/codex-code-review/references/codex-transport.md § Start with the explanation prompt. See references/codex-prompt-explain.md.

Depth Levels

Level	Description
brief	One-sentence summary
normal	Functional overview + execution flow + key concepts (default)
deep	+ Design patterns + complexity + issues + dependencies

Output

markdown

## Code Explanation: <target>
- **Depth**: brief / normal / deep
- **Summary**: <functional overview>
- **Execution flow**: <key paths>
- **Key concepts**: <patterns, abstractions>

Verification

Codex independently researched project context (imports, callers)
Explanation matches requested depth level
Key concepts are identified and explained

References

Explanation prompt: references/codex-prompt-explain.md

Examples

Input: /codex-explain src/service/order/order.service.ts
Action: Read file → Codex explain (normal) → Functional summary + detailed explanation

Input: /codex-explain src/service/xxx.ts --depth deep
Action: Read file → Codex explain (deep) → Patterns + complexity + issues

Input: /codex-explain src/xxx.ts --lines 50-100
Action: Read lines 50-100 → Codex explain → Focused explanation

Files

SKILL.md and 1 other file (references) in skills/codex-explain of sd0xdev/sd0x-harness.

SKILL.md
references/codex-prompt-explain.md

Open the folder on GitHubat commit a4d4bc1

Compare with similar skills

Codex Explain next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Codex Explain compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Codex Explain this skillsd0xdev/sd0x-harness	192	—	~560	Automated safety check: Pass	MIT	today
PR Babysitteropeninterpreter/openinterpreter	69k	3 repos	~4.2k	Automated safety check: Pass	Apache-2.0	yesterday
Code Review ChecklistshareAI-lab/learn-claude-code	78k	5 repos	~1.1k	Automated safety check: Pass	MIT	10 days ago
Backend Code Reviewlangflow-ai/langflow	156k	—	~3.5k	Automated safety check: Notes	MIT	today
Understand Diff AnalysisEgonex-AI/Understand-Anything	86k	1 repos	~1.4k	Automated safety check: Pass	MIT	2 days ago
Mole Bug Patternstw93/Mole	70k	—	~2k	Automated safety check: Pass	GPL-3.0	today

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69k GitHub starsUsed in 3 repos~4.2k tokens
DevelopmentAuto-check passed
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Questions about Codex Explain

What does Codex Explain do?

Explain complex code via Codex exec. An agent skill from sd0xdev/sd0x-harness. Codex Explain is an agent skill from sd0xdev/sd0x-harness. Explain complex code via Codex exec.

When should I use Codex Explain?

Codex Explain fits situations like: : understanding complex logic; tracing data flow; onboarding to unfamiliar code.

How do I install Codex Explain in Claude Code?

Run `npx skills add sd0xdev/sd0x-harness --skill codex-explain -a claude-code`. Or copy the skill folder (skills/codex-explain in sd0xdev/sd0x-harness) into .claude/skills/codex-explain in your project. Claude Code loads it when a task matches its description.

How do I install Codex Explain in Codex?

Run `npx skills add sd0xdev/sd0x-harness --skill codex-explain -a codex`. Or copy the skill folder (skills/codex-explain in sd0xdev/sd0x-harness) into .agents/skills/codex-explain in your project. Codex loads it when a task matches its description.

Can I use Codex Explain in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add sd0xdev/sd0x-harness --skill codex-explain -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/codex-explain, .gemini/skills/codex-explain, .github/skills/codex-explain and .opencode/skills/codex-explain in your project.

What does Codex Explain need to run?

SKILL.md names no scripts, command-line tools or credentials: Codex Explain is instructions for the agent only. Its frontmatter pre-approves these tools: Read, Grep, Glob, Bash(node:*), Write.

Does Codex Explain access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Codex Explain safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Codex Explain use?

Codex Explain is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Codex Explain use?

About 560 tokens (SKILL.md is roughly 2.2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 629 tokens, read only when the agent opens those files.

What are the alternatives to Codex Explain?

Skills that share tags, products or a category with Codex Explain: PR Babysitter (openinterpreter/openinterpreter, 69k stars), Code Review Checklist (shareAI-lab/learn-claude-code, 78k stars), Backend Code Review (langflow-ai/langflow, 156k stars) and Understand Diff Analysis (Egonex-AI/Understand-Anything, 86k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Codex Explain?

sd0xdev (a GitHub user) maintains it in sd0xdev/sd0x-harness, which has 192 GitHub stars. The repository holds 89 skills in this directory. The repository was last updated on October 8, 2026.

Source: sd0xdev/sd0x-harness on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Codex Explain

Facts

At a glance

What it does

When your agent uses it

Example prompts

Requirements

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Codex Explain Skill

Trigger

When NOT to Use

Workflow

Step 1: Read Target File

Step 2: Codex Explanation

Depth Levels

Output

Verification

References

Examples

Files

Compare with similar skills

Similar skills

More from sd0xdev/sd0x-harness

Related

Questions about Codex Explain