No way to send custom headers in claude_desktop_config.json

[jigarvyasidea]

Enhancement

Currently, the MCP client configuration (claude_desktop_config.json) only specifies which MCP server to run and how to connect to it.

{
  "mcpServers": {
    "jigar-mcp-server": {
      "command": "C:\\nylim\\mcp_project\\venv\\Scripts\\python.exe",
      "args": [
        "C:\\virtual_Protocol\\mcp_project\\mcp_server.py"
      ]
    }
  }
}

This works fine for starting the server, but there is no option to send custom headers or authentication tokens with the MCP client connection.

Problem:

Many real-world MCP server setups require auth headers / API keys / session IDs to validate the client.

Without a way to configure headers in the MCP client config, authentication becomes hard to implement.

Feature Request:
Add support in claude_desktop_config.json for passing custom headers (e.g., Authorization, Session-Id, User-Id).

Eg

{
  "mcpServers": {
    "Tejas-mcp-server": {
      "command": "C:\\nylim\\mcp_project\\venv\\Scripts\\python.exe",
      "args": [
        "C:\\nylim\\mcp_project\\mcp_server.py"
      ],
      "headers": {
        "Authorization": "Bearer <TOKEN>",
        "User-Id": "12345"
      }
    }
  }
}

Why important:

Enables secure authentication between MCP client and server.

Makes MCP more production-ready for enterprise and multi-user use cases.

[jlowin]

Does Claude Desktop support this?

[jigarvyasidea]

Yes @jlowin , this can be supported. In my project, I implemented it by creating a separate npx proxy that injects headers like Authorization, User-Id, and Session-Id. We also configure these headers in claude_desktop_config.json so Claude Desktop can send them to the MCP server like that .

[jlowin]

I think there is some confusion here. There is no concept of headers for a locally run server, and our install commands only install local servers.

[jigarvyasidea]

@jlowin I’m not talking about a locally run server. in Cloude_destop_config we make npx proxy and What I mean is that we make an HTTP request in that npx proxy and pass the required data in the request headers. On the MCP server side, we can then read it from request.headers. We can also configure and send these headers directly through the cloud_desktop_config.json file.

[jlowin]

The syntax you requested:

{
  "mcpServers": {
    "Tejas-mcp-server": {
      "command": "C:\\nylim\\mcp_project\\venv\\Scripts\\python.exe",
      "args": [
        "C:\\nylim\\mcp_project\\mcp_server.py"
      ],
      "headers": {
        "Authorization": "Bearer <TOKEN>",
        "User-Id": "12345"
      }
    }
  }
}

Is to my knowledge not supported by Claude Desktop, as this is the syntax for a local server which does not support headers. If you are using a proxy and a custom setup to achieve this, that's fine, but I do not understand what you are asking FastMCP to do. FastMCP's Claude Desktop integration is exclusively for adding local FastMCP servers, without a proxy, as that is challenging to do. We are not trying to be a generic tool for installing any server.

[HazemAbdesamed]

This was found in mcp-remote documentation. It worked for me.

{
  // rest of config...
  "args": [
    "mcp-remote",
    "https://remote.mcp.server/sse",
    "--header",
    "Authorization:${AUTH_HEADER}" // note no spaces around ':'
  ],
  "env": {
    "AUTH_HEADER": "Bearer <auth-token>" // spaces OK in env vars
  }
},