Lightbulb MCP Server

A Model Context Protocol (MCP) server implementation in Rust for managing a virtual lightbulb. This server provides tools to control and monitor a simulated lightbulb, with all actions logged to a file.

Features

• Get Status: Check if the lightbulb is currently on or off
• Turn On: Turn the lightbulb on (with logging)
• Turn Off: Turn the lightbulb off (with logging)
• Event Logging: All state changes are logged to lightbulb.log with timestamps

Available Tools

get_lightbulb_status

• Description: Get the current status of the lightbulb
• Parameters: None
• Returns: String indicating whether the lightbulb is on or off

turn_on_lightbulb

• Description: Turn on the lightbulb
• Parameters: None
• Returns: Success message or error if already on
• Side Effect: Logs the action to lightbulb.log

turn_off_lightbulb

• Description: Turn off the lightbulb
• Parameters: None
• Returns: Success message or error if already off
• Side Effect: Logs the action to lightbulb.log

Building and Running

Prerequisites

• Rust (latest stable version)
• Cargo

Build

cargo build

Run

cargo run

Log Format

The server logs all lightbulb actions to lightbulb.log in the following format:

[2025-08-02T14:24:27.652821025+00:00] Lightbulb turned ON
[2025-08-02T15:48:03.599625808+00:00] Lightbulb turned OFF

Technical Details

• Built using the rmcp crate for MCP protocol implementation
• Uses Arc<Mutex<bool>> for thread-safe state management
• Implements async tool handlers
• Uses chrono for RFC3339 timestamp formatting
• File I/O for persistent logging

Dependencies

• rmcp - MCP protocol implementation
• tokio - Async runtime
• chrono - Date/time handling
• serde & serde_json - Serialization

Testing

You can test the server manually by sending JSON-RPC requests via stdin:

{"jsonrpc": "2.0", "id": 1, "method": "initialize", "params": {}}
{"jsonrpc": "2.0", "id": 2, "method": "tools/list"}
{"jsonrpc": "2.0", "id": 3, "method": "tools/call", "params": {"name": "turn_on_lightbulb"}}