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mcp-websocket-invalid-protocol ​

WebSocket URLs should use ws:// or wss:// protocol

Warning

Rule Details ​

This rule parses the url field of MCP servers with type "ws" and checks that the protocol is ws: or wss:. Using an incorrect protocol such as http:// or https:// may cause connection failures or unexpected behavior. URLs containing variable expansions (${ or $) are skipped since they are resolved at runtime. Completely invalid URLs are caught by the mcp-websocket-invalid-url rule instead.

Incorrect ​

WebSocket server using https:// instead of wss://

json
{
  "mcpServers": {
    "realtime": {
      "type": "ws",
      "url": "https://mcp.example.com/ws"
    }
  }
}

Correct ​

WebSocket server using wss:// protocol

json
{
  "mcpServers": {
    "realtime": {
      "type": "ws",
      "url": "wss://mcp.example.com/ws"
    }
  }
}

WebSocket server using ws:// protocol for local development

json
{
  "mcpServers": {
    "local": {
      "type": "ws",
      "url": "ws://localhost:8080/ws"
    }
  }
}

How To Fix ​

Change the URL scheme to ws:// (unencrypted) or wss:// (encrypted). Use wss:// for production servers and ws:// only for local development.

Options ​

This rule does not have any configuration options.

Resources ​

Version ​

Available since: v0.2.0