# Implementation Summary: Hub Listing in Server Description
## Objective
Modify the `PlugwiseMcpServer` constructor to automatically list all hubs loaded from the `/hubs` folder in the server's description property, with a message instructing users to use the `add_hub` tool if they need to add more hubs.
## Changes Made
### 1. Updated Server Constructor
**File**: `/home/tom/plugwise/src/mcp/server.ts`
#### Added Imports
```typescript
import * as fs from 'fs';
import * as path from 'path';
```
#### Modified Constructor
The constructor now:
1. Initializes services first (before creating the Server instance)
2. Calls `getKnownHubsSync()` to load hub configurations
3. Formats the hub list using `formatHubsDescription()`
4. Appends the formatted hub list to the server description
### 2. New Private Methods
#### `getKnownHubsSync()`
Synchronously reads all `.json` files from the `/hubs` directory and extracts hub information.
**Returns**: `Array<{ name: string; ip: string }>`
**Features**:
- Gracefully handles missing `/hubs` directory (returns empty array)
- Skips invalid JSON files with error logging
- Extracts only `name` and `ip` fields for brevity and security
#### `formatHubsDescription()`
Formats the hub list into a human-readable string suitable for the server description.
**Parameters**: `hubs: Array<{ name: string; ip: string }>`
**Returns**: `string` - Formatted description appendix
**Output Format** (with hubs):
```
The hubs known now are listed below. If you are missing a hub, ask the user for the name of the hub and then use the add_hub tool to add it.
- Plugwise Gateway (192.168.178.235)
- Living Room Hub (192.168.1.100)
```
**Output Format** (no hubs):
```
The hubs known now are listed below. If you are missing a hub, ask the user for the name of the hub and then use the add_hub tool to add it.
- No hubs configured yet
```
## Testing
### Test Scripts Created
1. **`scripts/test-server-description.ts`** - Enhanced test with verification checks
2. **`scripts/test-hub-loading-simple.ts`** - Simple test showing hub loading
### Test Results
✅ Successfully loads existing hub files from `/hubs` folder
✅ Correctly formats hub information (name and IP)
✅ Appends formatted list to server description
✅ Gracefully handles empty `/hubs` directory
✅ No compile errors or runtime issues
### Example Output
When the server starts with one hub configured:
```
Plugwise MCP Server initialized - Smart Home Automation Control for AI Agents
Supports: Climate control, energy monitoring, switch automation, gateway management
Optimized for: Home automation workflows, energy optimization, comfort control
```
The server description now includes:
```
...automation routines, and integration with other smart home platforms. Supports network discovery, persistent hub management, real-time device state monitoring, and programmatic control of temperature, presets, and appliances.
The hubs known now are listed below. If you are missing a hub, ask the user for the name of the hub and then use the add_hub tool to add it.
- Plugwise Gateway (192.168.178.235)
```
## Benefits
1. **Immediate Context**: AI agents and coding assistants can see available hubs without additional API calls
2. **User Guidance**: Clear message about using add_hub for adding hubs
3. **Zero Runtime Overhead**: File reading happens once during server initialization
4. **Graceful Degradation**: Works correctly even when no hubs are configured
5. **Security**: Only exposes hub name and IP (not passwords or other sensitive data)
## Technical Notes
### Why Synchronous File I/O?
- TypeScript constructors cannot be `async`
- Server instance requires description at construction time
- Hub configuration files are small (typically < 1KB)
- One-time startup cost with negligible performance impact
- Simpler error handling and code flow
### File Structure
Hub files in `/hubs` are JSON format:
```json
{
"name": "Plugwise Gateway",
"ip": "192.168.178.235",
"password": "glmpttxf",
"model": "smile_open_therm",
"firmware": "3.7.8",
"discoveredAt": "2025-10-23T19:59:33.315Z"
}
```
Only `name` and `ip` are used in the description for security and brevity.
## Documentation Created
1. **`docs/server-description-hub-listing.md`** - Comprehensive feature documentation
2. **This summary** - Implementation overview
## Future Enhancements
Potential improvements:
- Add hub model/type to description
- Include online/offline status indicator
- Show last connection timestamp
- Support filtering by hub type
- Add cache to avoid repeated file reads on server restarts
## Related Files
- `/home/tom/plugwise/src/mcp/server.ts` - Main implementation
- `/home/tom/plugwise/src/services/hub-discovery.service.ts` - Hub loading service
- `/home/tom/plugwise/scripts/test-server-description.ts` - Verification test
- `/home/tom/plugwise/scripts/test-hub-loading-simple.ts` - Simple test
- `/home/tom/plugwise/docs/server-description-hub-listing.md` - Feature docs
- `/home/tom/plugwise/hubs/*.json` - Hub configuration files
## Verification Commands
Build the project:
```bash
npm run build
```
Run tests:
```bash
npx tsx scripts/test-hub-loading-simple.ts
npx tsx scripts/test-server-description.ts
```
Start the server and check description:
```bash
npm start
# The description with hub list is sent to MCP clients during initialization
```
