claudelint

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mcp-invalid-transport ​

MCP transport type must be one of the supported values

Error

Rule Details ​

This rule checks that the type field of each MCP server is one of the supported transport types: stdio, sse, http, streamable-http, or ws. An unrecognized transport type will prevent Claude Code from establishing a connection to the MCP server. Servers without an explicit type field are skipped because the type can be inferred from the presence of a command field.

Incorrect ​

Server with an unsupported transport type

json
{
  "mcpServers": {
    "my-server": {
      "type": "grpc",
      "url": "https://mcp.example.com"
    }
  }
}

Correct ​

Server with a valid HTTP transport type

json
{
  "mcpServers": {
    "my-server": {
      "type": "http",
      "url": "https://mcp.example.com"
    }
  }
}

Server with a valid stdio transport type

json
{
  "mcpServers": {
    "my-server": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@my/mcp-server"]
    }
  }
}

How To Fix ​

Change the type field to one of the supported values: stdio, sse, http, streamable-http, or ws. Note that sse is deprecated in favor of http, and that the WebSocket literal is "ws" - not "websocket", which is not a valid config value.

Options ​

This rule does not have any configuration options.

Resources ​

Version ​

Available since: v0.2.0