CLI Commands Reference

Claude Code

Add via CLI (recommended)

Serial:

claude mcp add --env SERIAL_PORT=/dev/ttyACM0 mcpu -- npx mcpu-client

WiFi TCP:

claude mcp add --env DEVICES=mydevice:192.168.1.42:3000:tcp mcpu -- npx mcpu-client

All options (--env, --scope, --transport) must come before the server name. The -- separator isolates the command passed to the MCP server.

Or edit .mcp.json (shared with team)

Serial:

{
  "mcpServers": {
    "mcpu": {
      "command": "npx",
      "args": ["mcpu-client"],
      "env": {
        "SERIAL_PORT": "/dev/ttyACM0"
      }
    }
  }
}

WiFi TCP:

{
  "mcpServers": {
    "mcpu": {
      "command": "npx",
      "args": ["mcpu-client"],
      "env": {
        "DEVICES": "mydevice:192.168.1.42:3000:tcp"
      }
    }
  }
}

Verify

claude mcp list

Or inside a Claude Code session: /mcp

---

Gemini CLI

Add via CLI (recommended)

Serial:

gemini mcp add -e SERIAL_PORT=/dev/ttyACM0 mcpu npx mcpu-client

WiFi TCP:

gemini mcp add -e DEVICES=mydevice:192.168.1.42:3000:tcp mcpu npx mcpu-client

Or edit ~/.gemini/settings.json directly

Serial:

{
  "mcpServers": {
    "mcpu": {
      "command": "npx",
      "args": ["mcpu-client"],
      "env": {
        "SERIAL_PORT": "/dev/ttyACM0"
      }
    }
  }
}

WiFi TCP:

{
  "mcpServers": {
    "mcpu": {
      "command": "npx",
      "args": ["mcpu-client"],
      "env": {
        "DEVICES": "mydevice:192.168.1.42:3000:tcp"
      }
    }
  }
}

Verify

gemini mcp list

Or inside a session: /mcp

---

OpenCode

OpenCode has no CLI add command — edit opencode.json directly.

Serial:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "mcpu": {
      "type": "local",
      "command": ["npx", "mcpu-client"],
      "enabled": true,
      "environment": {
        "SERIAL_PORT": "/dev/ttyACM0"
      }
    }
  }
}

WiFi TCP:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "mcpu": {
      "type": "local",
      "command": ["npx", "mcpu-client"],
      "enabled": true,
      "environment": {
        "DEVICES": "mydevice:192.168.1.42:3000:tcp"
      }
    }
  }
}

Note

OpenCode uses "environment" (not "env") and "command" must be an array.

Verify

opencode mcp list

---

Comparison Summary

	Claude Code	Gemini CLI	OpenCode
Add command	claude mcp add --env KEY=VAL mcpu -- npx mcpu-client	gemini mcp add -e KEY=VAL mcpu npx mcpu-client	manual config only
Config file	.mcp.json (project)	~/.gemini/settings.json	opencode.json
Env field	"env"	"env"	"environment"
Command format	string	string	array
Verify	claude mcp list / /mcp	gemini mcp list / /mcp	opencode mcp list

---

Finding Serial Port

OS	Typical port
Linux	/dev/ttyUSB0 or /dev/ttyACM0
macOS	/dev/cu.usbserial-*
Windows	COM3, COM4, …

# Linux / macOS
ls /dev/tty*

Windows: Device Manager → Ports (COM & LPT)