How to connect Claude, ChatGPT and Cursor to one source of truth

Setup steps for Claude, Claude Code, ChatGPT and Cursor on one MCP server, so every tool reads the same verified facts about your business.

Published:
By Neal Mann
Automation
How to connect Claude, ChatGPT and Cursor to one source of truth

Connect each tool to the same remote MCP server, https://mcp.getnoan.com/mcp, and every one of them reads the same verified facts. Claude, ChatGPT and Cursor each take that address in their own settings and sign in to NOAN once, and from then on a fact you change in one place is the fact all three read.

Why one source matters

Most teams end up with a copy of the truth in every tool. A project in Claude has the pricing pasted into its instructions. A custom GPT has the product sheet uploaded. Cursor has a rules file someone wrote at the start of the quarter. Each copy was right when it was made, and each one drifts on its own.

A fact layer replaces the copies with one address. NOAN holds your business facts, each verified by a named person, with every version kept. When a fact changes, the change reaches everything that reads it at once, so Claude, ChatGPT, Cursor and your own code never disagree about what your company decided.

Before you start

You need a NOAN account with some facts in it, and the address:

https://mcp.getnoan.com/mcp

The server speaks MCP over streamable HTTP. Clients that support OAuth open a NOAN sign-in the first time you connect, and you choose what the connection may read and write. Clients that take headers can send a NOAN API key as a bearer token instead.

Claude

  1. In Claude, open Settings, then Connectors.
  2. Add a custom connector. Name it NOAN and paste the address.
  3. Connect. Claude opens a NOAN sign-in, and your workspace's facts are available from the next message.

Claude Code

  1. In a terminal, add NOAN as an HTTP server:
claude mcp add --transport http noan https://mcp.getnoan.com/mcp
  1. In a session, type /mcp and pick NOAN to sign in.
  2. Ask for anything the facts know. Claude Code reads them before it answers or writes.

On a machine with no browser, pass a key instead of signing in by adding --header "Authorization: Bearer <NOAN API key>" to the same command.

ChatGPT

  1. In ChatGPT, open Settings, then Connectors, with developer mode on.
  2. Create a connector. Name it NOAN and paste https://mcp.getnoan.com/mcp.
  3. Sign in with your NOAN account when ChatGPT asks, then enable NOAN in a chat.

Cursor

  1. In Cursor, open Settings, then MCP, and add a new server. You can also edit .cursor/mcp.json directly.
  2. Add the server:
{
  "mcpServers": {
    "noan": {
      "url": "https://mcp.getnoan.com/mcp"
    }
  }
}
  1. Cursor asks you to sign in to NOAN once. Every agent run after that reads the facts.

Any other MCP client

Any client that takes an MCP server address over streamable HTTP can mount the same server. Where the client takes headers, send a key:

{
  "mcpServers": {
    "noan": {
      "url": "https://mcp.getnoan.com/mcp",
      "headers": { "Authorization": "Bearer <NOAN API key>" }
    }
  }
}

If you use several coding assistants on one machine, the NOAN wizard can set them up together. Run npx -y @getnoan/wizard@latest, and it takes your NOAN key, points each coding assistant on the machine at the address and installs the NOAN skill.

Your own code

Agents you build yourself can use the REST API at https://api.getnoan.com/v1 with a bearer key. It reads the same facts the MCP server serves:

curl "https://api.getnoan.com/v1/facts?block_slug=<your-block-slug>" \
  -H "Authorization: Bearer <NOAN API key>"

The full spec is at api.getnoan.com/openapi.json, and the API page explains the surface.

Decide what each connection may do

One source of truth does not mean every tool gets the same access. Through the MCP server, each area is scoped read or write on its own: facts, contacts, tasks, notes, assets and tags. A connection that can only read facts can answer from them and cannot change one. API keys are scoped per resource, read or write, can be limited to a list of allowed stacks, and can hold fact changes for approval, so anything an agent writes waits for a person to verify it before anything reads it.

A sensible starting point: read access to facts everywhere, and write access only where a person is reviewing the work.

Check that they agree

Ask Claude, ChatGPT and Cursor the same question about your business, for example what a plan includes. All three should give the same answer from the same fact. Then change that fact in NOAN, verify it, and ask again. The new version is current for every tool at once, and the old one is kept for history but no longer obeyed.

If one tool still gives the old answer, it is reading from a copy. Look for pasted instructions, uploaded files or rules files in that tool, remove the business facts from them, and replace them with one line:

For prices, policies and product details, read NOAN. If anything else disagrees with NOAN about the business, NOAN wins.

Next step

The MCP page has these steps with copy buttons for each client. Connect over MCP at https://mcp.getnoan.com/mcp, or over REST at https://api.getnoan.com/v1 with the OpenAPI spec. Or paste this into any agent:

Read https://www.getnoan.com/setup.md and follow it.

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