MCP server

https://auth.42six.ai/functions/v1/mcp

• Streamable HTTP, POST only, one JSON-RPC 2.0 message per request, protocol version 2025-06-18.
• Authorization: Bearer ftx_YOUR_KEY on every request. The key decides which workspace the tools read.
• Stateless: no session id is issued or required.
• Fourteen read tools under a key, listed on the Tool reference pages. A key never changes your books. No resources, no prompts.

A key works in clients that let you set a request header. ChatGPT, Claude.ai and other apps that sign in connect with OAuth instead of a key; see Signing in with 42six.

https://42six.ai/mcp

• An app that supports MCP sign-in (OAuth) connects to this address with no key: it sends you to 42six to sign in and approve it.
• You choose which books it reads, and whether it may propose changes to them. Changes start off.
• With changes on, the app also gets six change tools. Every change is a preview you confirm before it is applied; see Changes: preview and apply.
• Disconnect the app, or see what it can do, under Settings › Connected apps.

Add the server to ~/.cursor/mcp.json, or .cursor/mcp.json in a project:

{
  "mcpServers": {
    "fortytwosix": {
      "url": "https://auth.42six.ai/functions/v1/mcp",
      "headers": { "Authorization": "Bearer ftx_YOUR_KEY" }
    }
  }
}

Add the server to .vscode/mcp.json. VS Code asks for the key once and stores it, so it never sits in the file:

{
  "inputs": [
    { "type": "promptString", "id": "ftx-key", "description": "42six API key", "password": true }
  ],
  "servers": {
    "fortytwosix": {
      "type": "http",
      "url": "https://auth.42six.ai/functions/v1/mcp",
      "headers": { "Authorization": "Bearer ${input:ftx-key}" }
    }
  }
}

Any MCP client that supports Streamable HTTP and a custom header works: point it at the MCP URL and send Authorization: Bearer ftx_YOUR_KEY.