ext-apps/examples/scenario-modeler-server
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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.

Compare to Bootstrapped growth VC rocketship

MCP Client Configuration

Add to your MCP client configuration (stdio transport):

{
  "mcpServers": {
    "scenario-modeler": {
      "command": "npx",
      "args": [
        "-y",
        "--silent",
        "--registry=https://registry.npmjs.org/",
        "@modelcontextprotocol/server-scenario-modeler",
        "--stdio"
      ]
    }
  }
}

Local Development

To test local modifications, use this configuration (replace ~/code/ext-apps with your clone path):

{
  "mcpServers": {
    "scenario-modeler": {
      "command": "bash",
      "args": [
        "-c",
        "cd ~/code/ext-apps/examples/scenario-modeler-server && npm run build >&2 && node dist/index.js --stdio"
      ]
    }
  }
}

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

  1. Install dependencies:

    npm install
    
  2. Build and start the server:

    npm run start:http  # for Streamable HTTP transport
    # OR
    npm run start:stdio  # for stdio transport
    
  3. 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