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When you start a Hermes session, the extension automatically reads your editor’s MCP server configuration files and forwards every enabled server to Hermes as part of the session/new request. You do not need to duplicate your MCP setup — define your servers once in your editor config and Hermes picks them up automatically.

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Where MCP configs are read from

The extension checks four locations in the following order. Later entries override servers with the same name from earlier entries, so workspace-level configs take precedence over global configs.
LocationScope
~/.cursor/mcp.jsonGlobal Cursor MCP configuration
~/.vscode/mcp.jsonGlobal VS Code MCP configuration
<workspace>/.cursor/mcp.jsonWorkspace-level Cursor MCP configuration
<workspace>/.vscode/mcp.jsonWorkspace-level VS Code MCP configuration
All discovered and enabled servers are merged into a single list and passed to Hermes when the session starts. The extension also substitutes the following variables in command, args, env, and url fields before forwarding:
VariableResolves to
${workspaceFolder}The session working directory
${userHome}Your home directory
${env:NAME}The value of environment variable NAME

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Config format

Each mcp.json file uses the standard MCP server format. Place the file at one of the locations above and the extension discovers it automatically on the next session start.

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stdio server (most common)

{
  "mcpServers": {
    "my-server": {
      "command": "npx",
      "args": ["-y", "my-mcp-server"]
    }
  }
}

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stdio server with environment variables

{
  "mcpServers": {
    "my-server": {
      "command": "npx",
      "args": ["-y", "my-mcp-server", "--root", "${workspaceFolder}"],
      "env": {
        "API_KEY": "${env:MY_API_KEY}"
      }
    }
  }
}

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HTTP or SSE server

{
  "mcpServers": {
    "remote-server": {
      "type": "http",
      "url": "https://my-mcp-host.example.com/mcp",
      "headers": {
        "Authorization": "Bearer ${env:MCP_TOKEN}"
      }
    }
  }
}

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Disabling a server without removing it

Set "disabled": true on any server entry and the extension skips it when building the forwarded list. 
{
  "mcpServers": {
    "my-server": {
      "command": "npx",
      "args": ["-y", "my-mcp-server"],
      "disabled": true
    }
  }
}

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Verification

After you start a session, confirm your MCP servers were forwarded correctly:
  1. Send a message that would trigger one of your MCP servers.
  2. If hermes.showToolCalls is enabled, a tool call notification appears in the chat when Hermes invokes the server.
  3. If you see no tool calls and expect some, open the extension logs via the chat toolbar → More options → Logs and look for session/new to inspect the mcpServers payload that was sent.
MCP configurations are read once at session start. If you add, remove, or modify a server in your mcp.json after a session is already running, you must start a new session for the change to take effect. Use the + New Chat button in the toolbar or run Hermes: New Chat from the Command Palette.