Setting Up the Reteno Plugin for OpenAI Codex

The Reteno plugin for OpenAI Codex connects Codex directly to your Reteno account through an MCP connection — a protocol that lets AI agents communicate with external services and take actions on your behalf.

Once installed, you can manage email templates, contacts, segments, events, and analytics directly from Codex, without opening the Reteno platform. For a full list of what the agent can do, see Integrating Reteno with AI Agents.

When to choose OpenAI Codex over Claude Cowork: Codex is the better choice if you're comfortable using a terminal and prefer a code-first workflow. If you prefer a graphical interface without a terminal, Claude Cowork is an alternative that offers the same capabilities.

Requirements

• Access to Codex through a supported ChatGPT plan
• An active Reteno account

Installation

Step 1. Create a project folder

Choose your project source:

• Codex desktop app: create or select a local folder on your computer.
• Codex web: connect a GitHub repository.

Step 2. Install the plugin

Open your terminal and run the install command for your operating system.

macOS:

Install Reteno Plugin Marketplace
mkdir -p ~/.codex/plugins ~/.agents/plugins && git clone [email protected]:reteno-com/ai-plugin.git ~/.codex/plugins/reteno && cat > ~/.agents/plugins/marketplace.json <<'EOF'
{
"name": "reteno-plugins",
"interface": {
"displayName": "Built by Reteno"
},
"plugins": [
{
"name": "reteno",
"source": {
"source": "local",
"path": "./.codex/plugins/reteno"
},
"policy": {
"installation": "AVAILABLE",
"authentication": "ON_INSTALL"
},
"category": "Marketing"
}
]
}
EOF

Windows:

New-Item -ItemType Directory -Force "$HOME\.codex\plugins", "$HOME\.agents\plugins" | Out-Null

git clone [email protected]:reteno-com/ai-plugin.git "$HOME\.codex\plugins\reteno"

@'
{
  "name": "reteno-plugins",
  "interface": {
    "displayName": "Built by Reteno"
  },
  "plugins": [
    {
      "name": "reteno",
      "source": {
        "source": "local",
        "path": "./.codex/plugins/reteno"
      },
      "policy": {
        "installation": "AVAILABLE",
        "authentication": "ON_INSTALL"
      },
      "category": "Marketing"
    }
  ]
}
'@ | Set-Content "$HOME\.agents\plugins\marketplace.json"

Restart Codex. In the plugins list, find Built by Reteno and click Add to Codex — Install Reteno.

After installing the plugin, sign in to your Reteno account when prompted.

📘

Note

• When signing in for the first time, your browser may show a popup asking to allow access to apps on your device. Allow it — the Authenticate button in Codex will disappear after successful authorization. If the MCP connection is not available immediately, close and reopen Codex.

• After authentication, return to Codex, start a new thread in your project, and select Full access under the chat box.

  

Verify the Connection

To confirm the setup is working, ask the agent:

• Are any MCP servers connected?
• Can you list the available Reteno MCP tools?

If the agent confirms the Reteno MCP server is connected, try a first task:

• Show me my last 5 email templates.

What to Do Next

Once the plugin is connected, you can start working with your Reteno account through natural language. Some things to try:

• Show me the Open and Click metrics for all workflows last month.
• What is workflow ID 434661 about? Describe its structure.
• Translate email template ID 3935987 into German.

For more examples, see Working with Reteno Using AI Agents.

Troubleshooting

The "Built by Reteno" plugin doesn't appear after restarting Codex.

Check that the marketplace.json file was created correctly at ~/.agents/plugins/marketplace.json and that the plugin folder exists at ~/.codex/plugins/reteno. If either is missing, re-run the install command.

The Authenticate button doesn't disappear after signing in.

Close and reopen Codex completely. If the issue persists, go to Settings → MCP servers and check whether the Reteno server shows as connected.

The agent says no MCP servers are connected.

Start a new thread in your project folder and select Full access under the chat box. MCP connections are only active when Full access is enabled.

The plugin was installed but the agent doesn't know my Reteno account.

Go to Settings → MCP servers and verify that the Reteno server status is connected. If it shows as disconnected, click Authenticate and complete the sign-in flow again.