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Connecting Milestone MCP to OpenAI Codex

Add the Milestone MCP server to OpenAI Codex so Codex can interact with Milestone data during coding sessions.

MCP URL: https://app.mstone.ai/api/v1/mcp/

Prerequisites​

  • OpenAI Codex desktop app installed (version 26.x or later)
  • Access to app.mstone.ai with a valid account

Step 1: Edit config.toml​

Open the following file in any text editor:

~/.codex/config.toml

Scroll to the bottom and add the following block:

[mcp_servers.mstone]
url = "https://app.mstone.ai/api/v1/mcp/"

Save the file.

Step 2: Authenticate via OAuth​

Run the following command in Terminal to authenticate with your mstone.ai account:

codex mcp login mstone

A browser window will open. Sign in with your mstone.ai account. Once complete, you will see:

Successfully logged in to MCP server 'mstone'.

Step 3: Restart Codex​

Quit and reopen the Codex desktop app to load the new MCP server configuration.

Step 4: Verify the Connection​

In any new chat, type the following command to see all active MCP servers:

/mcp

Confirm that mstone appears in the list as connected.

Using Milestone in Codex​

Once connected, Codex will automatically use the Milestone MCP server when relevant. You can also:

  • Ask naturally — e.g. "Show me my AI spend for June 2026" and Codex will query Milestone.
  • Type /mcp in any chat to see active MCP servers and confirm mstone is listed.
  • Use @mstone explicitly in a prompt to invoke the server directly.