Example: SaaS Scenario Modeler

A React-based demo MCP App that lets users adjust SaaS business parameters and see real-time 12-month projections of revenue, costs, and profitability with comparison against pre-built scenario templates.

Features

Interactive Parameters: 5 sliders for Starting MRR, Growth Rate, Churn Rate, Gross Margin, and Fixed Costs
12-Month Projections: Line chart showing MRR, Gross Profit, and Net Profit over time
Scenario Templates: 5 pre-built business strategies (Bootstrapped, VC Rocketship, Cash Cow, Turnaround, Efficient Growth)
Template Comparison: Overlay dashed lines to compare your scenario against any template
Summary Metrics: Key metrics including Ending MRR, Total Revenue, Total Profit, and break-even month
Theme Support: Adapts to light/dark mode preferences

Running

Install dependencies:
```
npm install
```

Build and start the server:

npm run start:http  # for Streamable HTTP transport
# OR
npm run start:stdio  # for stdio transport

View using the basic-host example or another MCP Apps-compatible host.

Architecture

Server (`server.ts`)

Exposes a single get-scenario-data tool that returns:

5 pre-built scenario templates with parameters, projections, and summaries
Default input values for the sliders
Optionally computes custom projections when customInputs are provided

The tool is linked to a UI resource via _meta.ui.resourceUri.

App (`src/`)

Built with React for reactive slider updates and derived state management
Uses Chart.js for the line chart visualization
All projection calculations run client-side for instant slider feedback
Components: SliderRow, MetricCard, ProjectionChart
Template comparison shown as dashed overlay lines on the chart