How to integrate Fixer io MCP with Codex

Codex is one of the most popular coding harnesses out there. And MCP makes the experience even better. With Fixer io MCP integration, you can draft, triage, summarise emails, and much more, all without leaving the terminal or app, whichever you prefer.

Composio removes the Authentication handling completely from you. We handle the entire integration lifecycle, and all you need to do is just copy the URL below, authenticate inside Codex, and start using it.

Why use Composio?

Apart from a managed and hosted MCP server, you will get:

• CodeAct: A dedicated workbench that allows GPT to write its code to handle complex tool chaining. Reduces to-and-fro with LLMs for frequent tool calling.
• Large tool responses: Handle them to minimise context rot.
• Dynamic just-in-time access to 20,000 tools across 870+ other Apps for cross-app workflows. It loads the tools you need, so GPTs aren't overwhelmed by tools you don't need.

How to install Fixer io MCP in Codex

Codex CLI

Run the command in your terminal.

This will auto-redirect you to the Rube authentication page.

Once you're authenticated, you will be able to access the tools.

Verify the installation by running:

codex mcp list

If you otherwise prefer to use config.toml, add the following URL to it. You can get the bearer token from rube.app → Use Rube → MCP URL → Generate token

[projects."/home/user/composio"]
trust_level = "untrusted"

[mcp_servers.rube]
bearer_token_env_var = "your bearer token"
enabled = true
url = "https://rube.app/mcp"

Codex in VS Code

If you have installed Codex in VS Code.

Then: ⚙️ → MCP Settings → + Add servers → Streamable HTTP:

Add the Rube MCP URL: https://rube.app/mcp and the bearer token.

To verify, click on the Open config.toml

Make sure it's there:

[mcp_servers.composio_rube]
bearer_token_env_var = "your bearer token"
enabled = true
url = "https://rube.app/mcp"

Codex App

Codex App follows the same approach as VS Code.

1. Click ⚙️ on the bottom left → MCP Servers → + Add servers → Streamable HTTP:

2. Restart and verify if it's there in .codex/config.toml

[mcp_servers.composio_rube]
bearer_token_env_var = "your bearer token"
enabled = true
url = "https://rube.app/mcp"

3. Save, restart the extension, and start working.

The Fixer io MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Fixer io account. It provides structured and secure access to global currency exchange data, so your agent can perform actions like converting currencies, fetching historical rates, tracking exchange fluctuations, and listing supported symbols on your behalf.

• Real-time currency conversion: Instantly convert amounts between currencies using up-to-date or historical exchange rates with a single prompt.
• Fetch latest and historical rates: Let your agent retrieve the most recent exchange rates or get historical rates for any supported date to power financial analysis.
• Analyze currency fluctuations: Ask your agent to track and summarize day-to-day currency changes between two dates to monitor trends or volatility.
• Retrieve supported currency symbols: Quickly list all available currency codes and their full names to support app interfaces or custom workflows.
• Get exchange rate time series: Easily pull daily exchange rates over a custom period (up to 365 days) for detailed trend analysis or reporting.

Conclusion

You've successfully integrated Fixer io with Codex using Composio's Rube MCP server. Now you can interact with Fixer io directly from your terminal, VS Code, or the Codex App using natural language commands.

Key benefits of this setup:

• Seamless integration across CLI, VS Code, and standalone app
• Natural language commands for Fixer io operations
• Managed authentication through Composio's Rube
• Access to 20,000+ tools across 870+ apps for cross-app workflows
• CodeAct workbench for complex tool chaining

Next steps:

• Try asking Codex to perform various Fixer io operations
• Explore cross-app workflows by connecting more toolkits
• Build automation scripts that leverage Codex's AI capabilities