> Markdown version of [Codex](https://vaadin.com/docs/next/building-apps/agentic-development/mcp/supported-tools/codex). Section index: [llms.txt](https://vaadin.com/docs/next/building-apps/llms.txt)

# Codex

OpenAI Codex provides native support for HTTP-based MCP servers, making it straightforward to integrate with the Vaadin MCP server for enhanced code generation capabilities.

**Requirements:** Codex CLI version 0.43 or later

## <a id="recommended-install-via-the-vaadin-agent-marketplace"></a>Recommended: Install via the Vaadin Agent Marketplace

The easiest way to set up Codex for Vaadin development is the [Vaadin Skills](https://vaadin.com/docs/next/building-apps/agentic-development/agent-skills.md) plugin, which you install from the [Vaadin Agent Marketplace](https://github.com/vaadin/agent-marketplace). The plugin installs both the Vaadin MCP server and a set of Vaadin development skills. When you use the plugin, you don’t need to configure the MCP server manually as described below.

Installing the plugin requires a recent version of Codex with plugin support.

1. Add the marketplace:

   ```terminal
   codex plugin marketplace add vaadin/agent-marketplace --ref main
   ```

2. Install the plugin:

   ```terminal
   codex plugin add vaadin-skills@vaadin-marketplace
   ```

To preview the available plugins before installing, run `codex plugin list --marketplace vaadin-marketplace --available --json` (the `--available` flag requires `--json`).

To update the plugin later, upgrade the marketplace:

```terminal
codex plugin marketplace upgrade
```

If you prefer to connect only the MCP server, without the bundled skills, follow the manual configuration instructions below instead.

## <a id="manual-configuration"></a>Manual Configuration

Add the following to `~/.codex/config.toml`:

```toml
[mcp_servers.vaadin]
url = "https://mcp.vaadin.com/docs"
```

After configuration, restart Codex to load the new MCP server.

> **Note:** If you see "missing field command" errors, upgrade Codex with:
>
> ```bash
> npm install -g @openai/codex@latest
> ```

## <a id="configuration-file-format"></a>Configuration File Format

The Codex configuration uses TOML format:

- Each MCP server is defined under `[mcp_servers.name]`

- The `url` field points to the HTTP endpoint

- Multiple servers can be configured by adding additional sections

Example with multiple servers:

```toml
[mcp_servers.vaadin]
url = "https://mcp.vaadin.com/docs"

[mcp_servers.other_server]
url = "https://example.com/mcp"
```

## <a id="verify-the-setup"></a>Verify the Setup

After restarting Codex:

1. Start a new coding session

2. Ask Codex about Vaadin development (e.g., "Generate a Vaadin login form")

3. Codex queries the Vaadin MCP server to access relevant documentation

4. Generated code is based on current Vaadin best practices

You can verify active MCP servers by running:

```bash
codex mcp list
```

## <a id="resources"></a>Resources

- [Vaadin Agent Marketplace](https://github.com/vaadin/agent-marketplace)

- [Codex MCP Documentation](https://developers.openai.com/codex/mcp/)

- [Codex GitHub Repository](https://github.com/openai/codex)