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Connect AI tools to Letterhead (MCP)

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Letterhead’s Model Context Protocol (MCP) server lets AI assistants like Claude and ChatGPT securely access your Letterhead account. Once connected, you can ask questions about your channels, letters, and performance metrics in plain English, and the assistant answers using live data from your account.

What you can do with MCP

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  • Ask about channel and letter details
  • Review newsletter and campaign performance metrics
  • Explore curated content
  • Get subscriber and engagement statistics in plain English

Find your MCP server URL

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  1. In Letterhead, go to Settings → MCP.
  2. Under Server URL, click Copy URL. You’ll use this URL when adding Letterhead as a custom connector in your AI client.

Each company has its own MCP server URL, so copy it from your own account rather than reusing another company’s.

Connect your AI client

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The exact menu names vary by client, but the flow is the same in every one:

  1. Open your AI client. Open the AI assistant you want to connect (such as Claude or ChatGPT) and go to its connectors or integrations settings.
  2. Add Letterhead as a custom MCP server. Choose the option to add a custom connector or MCP server, then paste the server URL you copied above.
    • In Claude, this is typically under Settings → Connectors → Add custom connector.
    • In ChatGPT, look under Settings → Connectors.
  3. Sign in to Letterhead. When prompted, sign in to Letterhead using your normal login. Letterhead uses OAuth, so you’ll be redirected to authenticate and approve access for your AI client. You do not paste an API key — access is granted through this sign-in.

Once the connection is approved, your AI client can query your Letterhead account.

Troubleshooting

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  • Authorization error when signing in: The MCP server is available to company administrators only. Confirm you’re signing in with an admin account.
  • Connection failed: Re-copy the server URL from Settings → MCP and make sure you pasted the whole URL, including the trailing /mcp.
  • The connector prompts for an API key: The MCP connection uses OAuth sign-in, not an API key. If your client is asking for a key, make sure you added Letterhead as a custom MCP server / connector rather than a generic API integration.
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