# Example: Budget Allocator App
An interactive budget allocation tool demonstrating real-time data visualization with MCP Apps.
<table>
<tr>
<td><a href="https://modelcontextprotocol.github.io/ext-apps/screenshots/budget-allocator-server/01-initial.png"><img src="https://modelcontextprotocol.github.io/ext-apps/screenshots/budget-allocator-server/01-initial.png" alt="Initial" width="100%"></a></td>
<td><a href="https://modelcontextprotocol.github.io/ext-apps/screenshots/budget-allocator-server/02-over-budget.png"><img src="https://modelcontextprotocol.github.io/ext-apps/screenshots/budget-allocator-server/02-over-budget.png" alt="Over budget" width="100%"></a></td>
<td><a href="https://modelcontextprotocol.github.io/ext-apps/screenshots/budget-allocator-server/03-tech-heavy.png"><img src="https://modelcontextprotocol.github.io/ext-apps/screenshots/budget-allocator-server/03-tech-heavy.png" alt="Tech-heavy" width="100%"></a></td>
</tr>
</table>
## MCP Client Configuration
Add to your MCP client configuration (stdio transport):
```json
{
"mcpServers": {
"budget-allocator": {
"command": "npx",
"args": [
"-y",
"--silent",
"--registry=https://registry.npmjs.org/",
"@modelcontextprotocol/server-budget-allocator",
"--stdio"
]
}
}
}
```
### Local Development
To test local modifications, use this configuration (replace `~/code/ext-apps` with your clone path):
```json
{
"mcpServers": {
"budget-allocator": {
"command": "bash",
"args": [
"-c",
"cd ~/code/ext-apps/examples/budget-allocator-server && npm run build >&2 && node dist/index.js --stdio"
]
}
}
}
```
## Features
- **Interactive Sliders**: Adjust budget allocation across 5 categories (Marketing, Engineering, Operations, Sales, R&D)
- **Donut Chart**: Real-time visualization of allocation distribution using Chart.js
- **Sparkline Trends**: 24-month historical allocation data per category
- **Percentile Badges**: Compare your allocation vs. industry benchmarks
- **Stage Selector**: Switch between Seed, Series A, Series B, and Growth benchmarks
- **Budget Presets**: Quick selection of $50K, $100K, $250K, or $500K totals
## Running
1. Install dependencies:
```bash
npm install
```
2. Build and start the server:
```bash
npm run start:http # for Streamable HTTP transport
# OR
npm run start:stdio # for stdio transport
```
3. View using the [`basic-host`](https://github.com/modelcontextprotocol/ext-apps/tree/main/examples/basic-host) example or another MCP Apps-compatible host.
## Architecture
### Server (`server.ts`)
Exposes a single `get-budget-data` tool that returns:
- Category definitions with colors and default allocations
- Historical data (~120 data points) - 24 months of allocation history per category
- Industry benchmarks (~60 data points) - Aggregated percentile data by company stage
The tool is linked to a UI resource via `_meta.ui.resourceUri`.
### App (`src/mcp-app.ts`)
- Uses Chart.js for the donut chart visualization
- Renders sparkline trends using inline SVG
- Computes percentile rankings client-side from benchmark data
- Updates all UI elements reactively on slider changes
