How to integrate Simplero MCP with Codex

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Introduction

Codex is one of the most popular coding harnesses out there. And MCP makes the experience even better. With Simplero 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 Simplero MCP in Codex

Codex CLI

Run the command in your terminal.

Terminal

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

Rube authentication redirect 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.

VS Code MCP Settings

To verify, click on the Open config.toml

Open config toml in Codex

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:
Codex App MCP Settings
  1. 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"
  1. Save, restart the extension, and start working.

What is the Simplero MCP server, and what's possible with it?

The Simplero MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Simplero account. It provides structured and secure access so your agent can perform Simplero operations on your behalf.

Supported Tools & Triggers

Tools
Add Tag to ContactTool to add a tag to a contact identified by email address.
Bulk Subscribe to ListTool to add multiple subscribers to a list in a single asynchronous request (max 1,000 per request).
Create or Update AdministratorTool to create a new administratorship or update an existing one with the same email.
Create or Update ContactTool to create a new contact or update an existing contact with the same email.
Find Contact By EmailTool to find and retrieve a contact by email address.
Find Subscription By EmailTool to find subscriptions for a specific list by email address.
Get Administrator By IDTool to retrieve a single administratorship by internal ID.
Get AdministratorsTool to retrieve all administratorships for the account.
Get Admin RolesTool to retrieve all available admin roles for the account including custom roles.
Get Async Request StatusTool to check the status of an asynchronous API request.
Get Contact By IDTool to retrieve a JSON representation of a contact by internal ID.
Get InvoicesTool to get invoice information with optional filtering by date and invoice number.
Get All ListsTool to retrieve all mailing lists configured in the account.
Get ProductsTool to list all products in the account.
Remove AdministratorTool to delete an administratorship by ID.
Remove Tag from ContactTool to remove a tag from a contact identified by email address.
Subscribe to ListTool to add a new subscriber to a specific mailing list.
Unsubscribe From ListTool to unsubscribe a customer from a specific mailing list.
Update Contact CredentialsTool to update a contact's login credentials including email, first name, and last name.

Conclusion

You've successfully integrated Simplero with Codex using Composio's Rube MCP server. Now you can interact with Simplero 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 Simplero 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 Simplero operations
  • Explore cross-app workflows by connecting more toolkits
  • Build automation scripts that leverage Codex's AI capabilities

How to build Simplero MCP Agent with another framework

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Use Simplero MCP with Claude Agent SDK

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Use Simplero MCP with LlamaIndex

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Use Simplero MCP with CrewAI

Claude Code

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Use Simplero MCP with Claude Code

FAQ

What are the differences in Tool Router MCP and Simplero MCP?

With a standalone Simplero MCP server, the agents and LLMs can only access a fixed set of Simplero tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Simplero and many other apps based on the task at hand, all through a single MCP endpoint.

Can I use Tool Router MCP with Codex?

Yes, you can. Codex fully supports MCP integration. You get structured tool calling, message history handling, and model orchestration while Tool Router takes care of discovering and serving the right Simplero tools.

Can I manage the permissions and scopes for Simplero while using Tool Router?

Yes, absolutely. You can configure which Simplero scopes and actions are allowed when connecting your account to Composio. You can also bring your own OAuth credentials or API configuration so you keep full control over what the agent can do.

How safe is my data with Composio Tool Router?

All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Simplero data and credentials are handled as safely as possible.

Used by agents from

Context
Letta
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HubSpot
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Context
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glean
HubSpot
Agent.ai
Altera
DataStax
Entelligence
Rolai
Context
Letta
glean
HubSpot
Agent.ai
Altera
DataStax
Entelligence
Rolai

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