Ternary MCP for ChatGPT

This guide connects ChatGPT to your Ternary data. It applies to both chatgpt.com and the ChatGPT desktop app (macOS/Windows) — connectors belong to your ChatGPT account, so you set them up once and they work everywhere you're signed in, and the settings screens are the same in both. The mobile apps can use a connector you've already added, but adding one must happen on web or desktop.

In ChatGPT, custom MCP servers are added as plugins (ChatGPT's name for connectors), and what Ternary can do differs by mode:

This is a ChatGPT platform restriction, not a Ternary one: deep research connectors are limited by OpenAI to the search/fetch contract. For cost analysis, use developer mode.

Requirements

• A Ternary account (the email you use to sign in to Ternary).
• Developer mode enabled on your ChatGPT account (steps below). On Business/Enterprise/Edu workspaces, an admin may need to allow developer mode and custom plugins.

Step 1: Enable developer mode

Adding an unverified (custom) MCP server requires developer mode.

1. Open Settings → Security and login, and scroll to the Developer mode section — or use the Developer mode shortcut at the bottom of Settings → Plugins.
2. Turn the Developer mode toggle on. ChatGPT labels it "elevated risk" because it allows unverified servers; that warning is expected.

Step 2: Add Ternary as a plugin

1. Open the Plugins page from the left sidebar (or go to chatgpt.com/plugins).

2. Click Create app (top right — it only appears with developer mode on).

3. Fill in the New Plugin dialog:

   • Name: Ternary.
   • Connection: Server URL, with your region's server URL:
     • US: https://core-api.ternary.app/mcp
     • EU: https://core-api.eu.ternary.app/mcp
   • Authentication: OAuth (the default). Leave the advanced OAuth settings alone — they're discovered automatically.
   • Check the "I understand and want to continue" confirmation.

4. Click Create.

5. ChatGPT shows an Add Ternary to ChatGPT dialog — click Sign in with Ternary, log in with your Ternary credentials, and approve the access request.

The plugin's detail page now shows Connected on with the date.

Use it in a chat

1. Start a new chat.

2. Click the + button in the composer and pick Ternary from the menu to pin the plugin to your message.

3. Type your cost question, for example: "Which tenants can I access? Then show my top 5 services by spend for last month." — and send.

   You can also skip the menu and just mention Ternary in the prompt ("Using the Ternary plugin, …") — ChatGPT calls it automatically.

Because every Ternary tool is read-only, the default Allow low-risk actions permission runs them without confirmation prompts. ChatGPT lists your tenants, asks which one to query if needed, and reports the top services with the range total.

Good first prompts:

• "Which Ternary tenants can I access?"
• "Show my total cloud spend for last month, grouped by service."
• "Run a cost query for Q2 grouped by provider."

For deep research: start a Deep research run, add Ternary as a source, and ChatGPT will use search/fetch to pull in your saved reports as reference material.

OpenAI Codex (command line)

Codex is OpenAI's coding agent for the terminal. It connects to the same Ternary server as ChatGPT, but it is configured from the command line rather than the Plugins page, and it has no developer-mode step.

Codex needs version 0.148.0 or later. Earlier versions cannot sign in to Ternary.

codex mcp add ternary --url https://core-api.ternary.app/mcp

Use your region's URL: https://core-api.ternary.app/mcp for US, https://core-api.eu.ternary.app/mcp for EU.

That command detects the sign-in requirement and opens a Ternary page in your browser straight away. Log in and approve the access request. The session is remembered between runs.

If the browser does not open, or you need to sign in again later:

codex mcp login ternary

The equivalent entry in ~/.codex/config.toml, if you prefer to edit the file:

[mcp_servers.ternary]
url = "https://core-api.ternary.app/mcp"

Unlike ChatGPT's deep research mode, Codex has access to every Ternary tool.

Troubleshooting

• No "Create app" button on the Plugins page — developer mode is off. Enable it under Settings → Security and login → Developer mode.
• Plugin creation fails — verify the exact URL including the /mcp path and the right region, then retry once (a first attempt can time out while the service warms up).
• Sign-in fails — your email must belong to an existing Ternary user in that region. US and EU accounts are separate.
• "No tenants found" — your Ternary user has no explicit role on any tenant. Ask your Ternary admin to grant you a role.
• Only search and fetch appear — you're in deep research mode, which is limited to those two tools. Ask in a regular chat with the Ternary plugin enabled instead.
• ChatGPT asks for confirmation on every tool call — expected for unverified plugins; you can allow per-conversation.