Connect ChatMaxima MCP with Codex and ChatGPT

Overview

This guide shows how to connect ChatMaxima MCP with Codex and ChatGPT so OpenAI's tools can build chatbots, WhatsApp templates and WhatsApp Flows in your workspace. There are two products and both can use ChatMaxima MCP:

• Codex, OpenAI's coding agent, which reads MCP servers from its config file.
• ChatGPT, which supports custom connectors so the assistant can call external tools.

Both use the same ChatMaxima MCP URL and the same secure OAuth 2.1 sign-in, so you never paste an API key.

Prerequisites

Before you begin, ensure you have:

• A ChatMaxima account with a role that can use the builder, templates or Flows.
• Codex installed, or a ChatGPT plan that supports custom connectors.
• The MCP URL: https://chatmaxima.com/mcp

Option A: Connect with Codex

Codex reads MCP servers from its configuration file, usually ~/.codex/config.toml.

Step 1: Open the Codex config

Open ~/.codex/config.toml. Create it if it does not exist.

Step 2: Add the ChatMaxima MCP server

ChatMaxima is a remote streamable HTTP server with OAuth. The most compatible way to add a remote MCP server in Codex is through the mcp-remote bridge, which handles the OAuth sign-in:

[mcp_servers.chatmaxima]
command = "npx"
args = ["-y", "mcp-remote", "https://chatmaxima.com/mcp"]

Note: The mcp-remote bridge opens your browser for the ChatMaxima sign-in the first time it runs, then caches the connection. If your version of Codex supports remote HTTP MCP servers directly, you can point it at https://chatmaxima.com/mcp instead of using the bridge.

Step 3: Sign in and build

1. Start Codex. On first use it opens the ChatMaxima consent screen in your browser.
2. Sign in, choose your workspace, and click Approve.
3. Ask Codex to build, for example: "Using ChatMaxima, create a lead capture bot and run a test."

Option B: Connect with ChatGPT

ChatGPT can use ChatMaxima MCP as a custom connector.

Step 1: Open connector settings

1. Open ChatGPT.
2. Go to Settings, then Connectors.
3. If custom connectors are behind an advanced or developer option, enable it.

Step 2: Add ChatMaxima

1. Choose to add a custom connector.
2. Enter a name, for example ChatMaxima.
3. Paste the MCP server URL:

https://chatmaxima.com/mcp

4. Confirm to add it.

Step 3: Sign in and pick your workspace

1. Start the connection. ChatGPT opens the ChatMaxima consent screen.
2. Sign in to ChatMaxima.
3. Choose the workspace you want to connect.
4. Review the access and click Approve.

Step 4: Use it in a chat

1. Start a chat and enable the ChatMaxima connector.
2. Ask it to build, for example: "Using ChatMaxima, compose an appointment reminder WhatsApp template with the customer name and date as variables."

What you can do once connected

Task	Example request
Build a chatbot	"Build an FAQ bot for a SaaS product and test it."
Compose a WhatsApp template	"Compose a payment received WhatsApp template."
Design a WhatsApp Flow	"Create a WhatsApp Flow for event registration."
Inspect existing bots	"List my chatbots and describe the support bot."

The tools available depend on your role in the selected workspace. See What is ChatMaxima MCP for details.

Manage or revoke access

• In Codex: remove the [mcp_servers.chatmaxima] block from config.toml.
• In ChatGPT: open Settings, then Connectors, and remove ChatMaxima.
• In ChatMaxima: open Settings, then Connected Apps, and revoke the connection. It stops working immediately.

Troubleshooting

Codex does not load the server

1. Confirm the TOML block is correct and the URL is https://chatmaxima.com/mcp.
2. Confirm npx is available if you use the mcp-remote bridge.
3. Restart Codex so it reloads the config.

ChatGPT does not show ChatMaxima tools

1. Confirm your plan supports custom connectors and that the connector is enabled for the chat.
2. Disconnect and reconnect so the tool list refreshes.

Sign-in does not complete

1. Allow your browser to open the ChatMaxima consent window.
2. Start the connection again and finish the sign-in.

No tools appear after connecting

1. Confirm your role in the selected workspace has builder, template or Flow access.
2. Reconnect and select the correct workspace.

Next Steps

• Create a Chatbot with MCP →
• Connect with Claude →
• Connect with Gemini →