How to use Roblox MCP with Google Gemini CLI.

Prerequisites

Node.js (v18.0.0 or higher)
```
node --version
```
Gemini CLI installed
```
npm install -g @google/gemini-cli
```
Roblox Studio plugin installation complete

Registering the MCP Server

Method 1: CLI Command (Recommended)

gemini mcp add weppy-roblox-mcp npx --trust -- -y @weppy/roblox-mcp

The --trust flag skips the confirmation prompt on each tool call.

To register as a global setting, add -s user:

gemini mcp add weppy-roblox-mcp npx -s user --trust -- -y @weppy/roblox-mcp

Method 2: Edit Config File

Add the following to your .gemini/settings.json file:

{
  "mcpServers": {
    "weppy-roblox-mcp": {
      "command": "npx",
      "args": ["-y", "@weppy/roblox-mcp"]
    }
  }
}

Config file location:

Scope	Path
Project	`<project>/.gemini/settings.json`
Global	`~/.gemini/settings.json`

Method 3: Using Environment Variables

When specific environment variables are needed:

CLI:

gemini mcp add weppy-roblox-mcp npx --trust -e HTTP_PORT=3002 -- -y @weppy/roblox-mcp

Config file:

{
  "mcpServers": {
    "weppy-roblox-mcp": {
      "command": "npx",
      "args": ["-y", "@weppy/roblox-mcp"],
      "env": {
        "HTTP_PORT": "3002"
      }
    }
  }
}

Connection Test

Launch Roblox Studio → Plugins tab → WEPPY → Connect

Run Gemini CLI and enter:

Tell me what is currently selected in Roblox Studio

Checking MCP Server Status

Use the /mcp command inside Gemini CLI to check the status of connected servers:

/mcp

Troubleshooting

Server Won’t Start

Run the MCP server directly to see the error:

npx -y @weppy/roblox-mcp

Connection Fails

Confirm the Roblox Studio plugin shows Connected status
Check that port 3002 is not blocked by a firewall
Check server status with the /mcp command

Tool Name Conflicts

If multiple MCP servers have tools with the same name, the tool names are prefixed in serverAlias__toolName format.

Gemini CLI Setup