How to integrate Mercury MCP with Codex

Connect Codex to Mercury MCP. List mercury accounts and current balances, summarize recent mercury card transactions, and more using natural language, with authentication handled for you.

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Mercury MCP is Mercury's official MCP server for read-only business banking data. Use it to safely inspect accounts, balances, transactions, cards, statements, and treasury data.

30 Tools

Introduction

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

Also integrate Mercury MCP with

Claude Cowork

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 1000+ 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 Mercury MCP in Codex

Run the setup command

Run this command in your terminal to add the Composio MCP server to Codex.

Terminal

It will initiate the authentication in a browser window, authorize Codex to access your Composio account.

Composio authentication page

(Optional) Authenticate with OAuth

To authenticate manually, run the login command to open a browser window and authorize Codex to access your Composio account.

bash
codex mcp login composio

Verify the connection

Run codex mcp list to confirm Composio appears as a registered MCP server.

bash
codex mcp list

Codex App

Codex App follows the same approach as VS Code.

  1. Click ⚙️ on the bottom left → MCP Servers → + Add servers → Streamable HTTP:
  2. Fill the header and Key fields with { "x-consumer-api-key" = "ck_*******" }.
  3. The Key is the Composio API key, that you can find on dashboard.composio.dev
  4. Click on Authenticate and authorize Codex to your Composio account and you're all set.
Codex App MCP setup
  1. Restart and verify if it's there in .codex/config.toml
bash
[mcp_servers.composio]
url = "https://connect.composio.dev/mcp"
http_headers = { "x-consumer-api-key" = "ck_*******" }

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

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

Conclusion

You've successfully integrated Mercury with Codex using Composio's MCP server. Now you can interact with Mercury 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 Mercury operations
  • Managed authentication through Composio
  • Access to 20,000+ tools across 1000+ apps for cross-app workflows
  • CodeAct workbench for complex tool chaining

Next steps:

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

Supported Tools

Every Mercury MCP action and event your agent gets out of the box.

Getaccount

Get account by ID

Getaccountcards

Retrieve all debit and credit cards associated with a specific account.

Getaccounts

Retrieve a paginated list of accounts.

Getaccountstatements

Retrieve a paginated list of monthly statements for a specific account.

Getattachment

Retrieve attachment details including download URL

Getcurrentdate

Get the current date in the format.

Getcustomer

Retrieve details of a specific customer by their ID

Getinvoice

Retrieve details of an invoice by its ID

Getorganization

Retrieve information about your organization including EIN, legal business name, and DBAs.

Getrecipient

Retrieve details of a specific recipient by ID

Getrecipients

Retrieve a paginated list of all recipients.

Getsaferequest

Retrieve a specific SAFE request by its ID.

Getsaferequests

Retrieve all SAFE (Simple Agreement for Future Equity) requests for your organization.

Gettransaction

Get transaction by ID

Gettransactionbyid

Retrieve a single transaction by its ID.

Gettreasury

Retrieve a paginated list of all treasury accounts associated with the authenticated organization.

Gettreasurystatements

Retrieve a paginated list of statements for a specific treasury account.

Gettreasurytransactions

Retrieve paginated treasury transactions for a specific treasury account.

Getuser

Get user by ID

Getusers

Get all users

Getwebhook

Retrieve details of a specific webhook endpoint by ID

Getwebhooks

Retrieve a paginated list of all webhook endpoints for your organization.

Listcategories

Retrieve a paginated list of all available custom expense categories for the organization.

Listcredit

Retrieve a list of all credit accounts for the organization.

Listcustomers

Retrieve a paginated list of customers.

Listinvoiceattachments

Retrieve a list of all attachments for a specific invoice

Listinvoices

Retrieve a paginated list of invoices.

Listrecipientsattachments

Retrieve a paginated list of all recipient tax form attachments across all recipients in the organization.

Listsendmoneyapprovalrequests

Retrieve a paginated list of send money approval requests for the authenticated organization.

Listtransactions

Retrieve a paginated list of all transactions across all accounts.

FRAMEWORKS

How to build Mercury MCP Agent with another framework

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Claude Cowork

Use Mercury MCP with Claude Cowork

FAQ

Frequently asked questions

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

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 Mercury tools.

Yes, absolutely. You can configure which Mercury 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.

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 Mercury data and credentials are handled as safely as possible.

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