# How to Explain Existing Code with the OpenAI Codex Plugin > Learn how to use the OpenAI Codex plugin to explain existing code with review commands and custom skills. Understand your codebase faster. - Repository: [OpenAI/codex-plugin-cc](https://github.com/openai/codex-plugin-cc) - Tags: how-to-guide - Published: 2026-07-03 --- **Yes, the Codex plugin can explain existing code by leveraging its review commands (`/codex:review`, `/codex:adversarial-review`) and custom skills architecture, even though it does not expose a dedicated "explain" command.** The openai/codex-plugin-cc repository extends Claude Code with OpenAI's Codex capabilities. While the plugin lacks a standalone "explain code" slash command, it generates detailed natural-language explanations of any repository by utilizing the same underlying review machinery that powers its code analysis features. ## How the Codex Plugin Generates Code Explanations ### Architecture Overview The plugin functions as a thin wrapper around the locally-installed Codex CLI. In `plugins/codex/scripts/lib/codex.mjs`, the wrapper forwards slash-command payloads to the Codex binary and surfaces JSON-formatted output back to Claude Code. This architecture allows any command—including reviews—to return explanatory text about code functionality. ### Review Commands as Explanation Engines The primary entry points for code explanations are `/codex:review` and `/codex:adversarial-review`. These commands invoke Codex to analyze current uncommitted changes or branch diffs. The review output contains sentence-level descriptions of what the code does, why specific patterns are used, and potential issues, effectively serving as a comprehensive explanation. ## Methods to Explain Code with the Codex Plugin ### Immediate Explanations with /codex:review Run a foreground review to get instant explanations of your current changes: ```bash # Explain the current changes (read-only) /codex:review ``` This prints a natural-language description of the examined code directly in your terminal. ### Background Analysis and Result Retrieval For large diffs or complex codebases, run the review asynchronously: ```bash # Start a review in the background /codex:review --background # Check progress /codex:status # Retrieve the explanatory output /codex:result ``` The `/codex:result` command displays the stored Codex response containing the detailed explanation. ### Targeted Explanations via /codex:adversarial-review Use the adversarial review command to focus on specific files or design aspects: ```bash # Ask Codex to focus on a particular module /codex:adversarial-review --background explain the purpose of the `state` module ``` This steerable approach allows you to request focused explanations of specific architecture components. ### Creating Custom Explanation Skills Because the plugin routes all commands through the `codex.mjs` wrapper, you can create custom skills that explicitly ask for explanations. Create a skill file at [`plugins/codex/skills/explain-code/SKILL.md`](https://github.com/openai/codex-plugin-cc/blob/main/plugins/codex/skills/explain-code/SKILL.md): ```markdown Explain what the function `processChanges` does and why it uses a queue. ``` The wrapper forwards this prompt to the Codex CLI, which returns the explanatory text via the standard result mechanism. ## Key Implementation Files Understanding these source files helps when building custom explanation workflows: - **`plugins/codex/scripts/lib/codex.mjs`**: Core wrapper that invokes the local Codex CLI and returns output to Claude Code. - **[`plugins/codex/commands/review.md`](https://github.com/openai/codex-plugin-cc/blob/main/plugins/codex/commands/review.md)**: Specification for the `/codex:review` command that generates code explanations. - **[`plugins/codex/commands/adversarial-review.md`](https://github.com/openai/codex-plugin-cc/blob/main/plugins/codex/commands/adversarial-review.md)**: Specification for steerable reviews targeting specific explanation requests. - **[`plugins/codex/commands/result.md`](https://github.com/openai/codex-plugin-cc/blob/main/plugins/codex/commands/result.md)**: Retrieves stored Codex output containing the actual explanations. - **[`README.md`](https://github.com/openai/codex-plugin-cc/blob/main/README.md)**: Documents all slash commands and their explanation capabilities. ## Summary - The Codex plugin explains existing code through its review commands rather than a dedicated "explain" command. - **`/codex:review`** and **`/codex:adversarial-review`** analyze code and return natural-language descriptions of functionality and design patterns. - The **`codex.mjs`** wrapper forwards all requests to the Codex CLI, making the system extensible via custom skills. - Use **`/codex:result`** to retrieve explanations from background reviews. - Custom skills can be built to ask specific "explain this" questions by leveraging the underlying wrapper architecture. ## Frequently Asked Questions ### Does the Codex plugin have a dedicated /codex:explain command? No. While there is no standalone `/codex:explain` command, the **`/codex:review`** and **`/codex:adversarial-review`** commands produce detailed natural-language explanations of code as part of their review output. You can also create custom skills that explicitly ask Codex to explain specific functions or modules. ### How do I get an explanation of code that isn't in my current changes? Use **`/codex:adversarial-review`** with a specific prompt targeting the file or module you want explained. For example, you can specify "explain the purpose of the `state` module" to get a focused explanation of code not necessarily in your uncommitted changes. ### Can I save or reuse specific explanation prompts? Yes. Create a custom skill in the `plugins/codex/skills/` directory with a [`SKILL.md`](https://github.com/openai/codex-plugin-cc/blob/main/SKILL.md) file containing your explanation prompt. The `codex.mjs` wrapper will forward this prompt to Codex just like any other command, allowing you to reuse specific explanation requests across your team. ### What's the difference between foreground and background reviews for code explanation? Foreground reviews (default **`/codex:review`**) run synchronously and display explanations immediately, suitable for smaller diffs. Background reviews (using the **`--background`** flag) run asynchronously via the Codex app-server, allowing you to check status with **`/codex:status`** and retrieve results later with **`/codex:result`**, which is ideal for large codebases or complex architectural explanations.