Add scenario-modeler-server example
Demo MCP App for SaaS financial planning with: - Interactive sliders for MRR, growth, churn, margin, and costs - 12-month projection charts (MRR, Gross Profit, Net Profit) - 5 pre-built scenario templates (Bootstrapped, VC Rocketship, etc.) - Template comparison overlay for strategy analysis - Light/dark theme support 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
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Jonathan Hefner
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examples/scenario-modeler-server/server.ts
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examples/scenario-modeler-server/server.ts
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import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
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import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
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import type {
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CallToolResult,
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ReadResourceResult,
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} from "@modelcontextprotocol/sdk/types.js";
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import cors from "cors";
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import express, { type Request, type Response } from "express";
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import fs from "node:fs/promises";
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import path from "node:path";
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import { z } from "zod";
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import { RESOURCE_URI_META_KEY } from "../../dist/src/app";
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const PORT = process.env.PORT ? parseInt(process.env.PORT, 10) : 3001;
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const DIST_DIR = path.join(import.meta.dirname, "dist");
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// ============================================================================
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// Schemas - types are derived from these using z.infer
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// ============================================================================
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const ScenarioInputsSchema = z.object({
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startingMRR: z.number(),
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monthlyGrowthRate: z.number(),
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monthlyChurnRate: z.number(),
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grossMargin: z.number(),
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fixedCosts: z.number(),
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});
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const MonthlyProjectionSchema = z.object({
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month: z.number(),
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mrr: z.number(),
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grossProfit: z.number(),
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netProfit: z.number(),
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cumulativeRevenue: z.number(),
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});
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const ScenarioSummarySchema = z.object({
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endingMRR: z.number(),
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arr: z.number(),
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totalRevenue: z.number(),
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totalProfit: z.number(),
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mrrGrowthPct: z.number(),
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avgMargin: z.number(),
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breakEvenMonth: z.number().nullable(),
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});
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const ScenarioTemplateSchema = z.object({
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id: z.string(),
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name: z.string(),
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description: z.string(),
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icon: z.string(),
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parameters: ScenarioInputsSchema,
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projections: z.array(MonthlyProjectionSchema),
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summary: ScenarioSummarySchema,
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keyInsight: z.string(),
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});
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const GetScenarioDataInputSchema = z.object({
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customInputs: ScenarioInputsSchema.optional().describe(
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"Custom scenario parameters to compute projections for",
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),
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});
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const GetScenarioDataOutputSchema = z.object({
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templates: z.array(ScenarioTemplateSchema),
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defaultInputs: ScenarioInputsSchema,
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customProjections: z.array(MonthlyProjectionSchema).optional(),
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customSummary: ScenarioSummarySchema.optional(),
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});
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// Types derived from schemas
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type ScenarioInputs = z.infer<typeof ScenarioInputsSchema>;
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type MonthlyProjection = z.infer<typeof MonthlyProjectionSchema>;
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type ScenarioSummary = z.infer<typeof ScenarioSummarySchema>;
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type ScenarioTemplate = z.infer<typeof ScenarioTemplateSchema>;
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// ============================================================================
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// Calculations
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// ============================================================================
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function calculateProjections(inputs: ScenarioInputs): MonthlyProjection[] {
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const {
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startingMRR,
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monthlyGrowthRate,
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monthlyChurnRate,
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grossMargin,
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fixedCosts,
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} = inputs;
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const netGrowthRate = (monthlyGrowthRate - monthlyChurnRate) / 100;
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const projections: MonthlyProjection[] = [];
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let cumulativeRevenue = 0;
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for (let month = 1; month <= 12; month++) {
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const mrr = startingMRR * Math.pow(1 + netGrowthRate, month);
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const grossProfit = mrr * (grossMargin / 100);
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const netProfit = grossProfit - fixedCosts;
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cumulativeRevenue += mrr;
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projections.push({
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month,
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mrr,
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grossProfit,
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netProfit,
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cumulativeRevenue,
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});
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}
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return projections;
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}
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function calculateSummary(
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projections: MonthlyProjection[],
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inputs: ScenarioInputs,
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): ScenarioSummary {
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const endingMRR = projections[11].mrr;
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const arr = endingMRR * 12;
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const totalRevenue = projections.reduce((sum, p) => sum + p.mrr, 0);
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const totalProfit = projections.reduce((sum, p) => sum + p.netProfit, 0);
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const mrrGrowthPct =
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((endingMRR - inputs.startingMRR) / inputs.startingMRR) * 100;
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const avgMargin = (totalProfit / totalRevenue) * 100;
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const breakEvenProjection = projections.find((p) => p.netProfit >= 0);
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const breakEvenMonth = breakEvenProjection?.month ?? null;
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return {
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endingMRR,
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arr,
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totalRevenue,
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totalProfit,
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mrrGrowthPct,
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avgMargin,
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breakEvenMonth,
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};
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}
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function calculateScenario(inputs: ScenarioInputs) {
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const projections = calculateProjections(inputs);
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const summary = calculateSummary(projections, inputs);
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return { projections, summary };
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}
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function buildTemplate(
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id: string,
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name: string,
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description: string,
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icon: string,
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parameters: ScenarioInputs,
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keyInsight: string,
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): ScenarioTemplate {
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const { projections, summary } = calculateScenario(parameters);
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return {
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id,
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name,
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description,
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icon,
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parameters,
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projections,
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summary,
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keyInsight,
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};
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}
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// ============================================================================
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// Pre-defined Templates
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// ============================================================================
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const SCENARIO_TEMPLATES: ScenarioTemplate[] = [
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buildTemplate(
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"bootstrapped",
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"Bootstrapped Growth",
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"Low burn, steady growth, path to profitability",
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"🌱",
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{
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startingMRR: 30000,
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monthlyGrowthRate: 4,
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monthlyChurnRate: 2,
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grossMargin: 85,
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fixedCosts: 20000,
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},
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"Profitable by month 1, but slower scale",
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),
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buildTemplate(
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"vc-rocketship",
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"VC Rocketship",
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"High burn, explosive growth, raise more later",
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"🚀",
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{
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startingMRR: 100000,
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monthlyGrowthRate: 15,
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monthlyChurnRate: 5,
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grossMargin: 70,
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fixedCosts: 150000,
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},
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"Loses money early but ends at 3x MRR",
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),
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buildTemplate(
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"cash-cow",
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"Cash Cow",
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"Mature product, high margin, stable revenue",
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"🐄",
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{
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startingMRR: 80000,
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monthlyGrowthRate: 2,
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monthlyChurnRate: 1,
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grossMargin: 90,
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fixedCosts: 40000,
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},
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"Consistent profitability, low risk",
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),
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buildTemplate(
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"turnaround",
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"Turnaround",
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"Fighting churn, rebuilding product-market fit",
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"🔄",
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{
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startingMRR: 60000,
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monthlyGrowthRate: 6,
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monthlyChurnRate: 8,
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grossMargin: 75,
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fixedCosts: 50000,
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},
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"Negative net growth requires urgent action",
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),
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buildTemplate(
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"efficient-growth",
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"Efficient Growth",
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"Balanced approach with sustainable economics",
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"⚖️",
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{
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startingMRR: 50000,
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monthlyGrowthRate: 8,
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monthlyChurnRate: 3,
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grossMargin: 80,
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fixedCosts: 35000,
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},
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"Good growth with path to profitability",
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),
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];
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const DEFAULT_INPUTS: ScenarioInputs = {
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startingMRR: 50000,
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monthlyGrowthRate: 5,
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monthlyChurnRate: 3,
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grossMargin: 80,
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fixedCosts: 30000,
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};
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// ============================================================================
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// Formatters for text output
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// ============================================================================
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function formatCurrency(value: number): string {
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const absValue = Math.abs(value);
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const sign = value < 0 ? "-" : "";
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if (absValue >= 1_000_000) {
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return `${sign}$${(absValue / 1_000_000).toFixed(2)}M`;
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}
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if (absValue >= 1_000) {
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return `${sign}$${(absValue / 1_000).toFixed(1)}K`;
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}
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return `${sign}$${Math.round(absValue)}`;
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}
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function formatScenarioSummary(
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summary: ScenarioSummary,
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label: string,
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): string {
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return [
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`${label}:`,
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` Ending MRR: ${formatCurrency(summary.endingMRR)}`,
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` ARR: ${formatCurrency(summary.arr)}`,
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` Total Revenue: ${formatCurrency(summary.totalRevenue)}`,
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` Total Profit: ${formatCurrency(summary.totalProfit)}`,
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` MRR Growth: ${summary.mrrGrowthPct.toFixed(1)}%`,
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` Break-even: ${summary.breakEvenMonth ? `Month ${summary.breakEvenMonth}` : "Not achieved"}`,
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].join("\n");
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}
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// ============================================================================
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// MCP Server
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// ============================================================================
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const server = new McpServer({
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name: "SaaS Scenario Modeler",
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version: "1.0.0",
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});
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// Register tool and resource
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{
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const resourceUri = "ui://scenario-modeler/mcp-app.html";
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server.registerTool(
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"get-scenario-data",
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{
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title: "Get Scenario Data",
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description:
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"Returns SaaS scenario templates and optionally computes custom projections for given inputs",
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inputSchema: GetScenarioDataInputSchema.shape,
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outputSchema: GetScenarioDataOutputSchema.shape,
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_meta: { [RESOURCE_URI_META_KEY]: resourceUri },
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},
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async (args: {
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customInputs?: ScenarioInputs;
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}): Promise<CallToolResult> => {
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const customScenario = args.customInputs
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? calculateScenario(args.customInputs)
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: undefined;
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const text = [
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"SaaS Scenario Modeler",
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"=".repeat(40),
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"",
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"Available Templates:",
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...SCENARIO_TEMPLATES.map(
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(t) => ` ${t.icon} ${t.name}: ${t.description}`,
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),
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"",
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customScenario
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? formatScenarioSummary(customScenario.summary, "Custom Scenario")
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: "Use customInputs parameter to compute projections for a specific scenario.",
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].join("\n");
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return {
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content: [{ type: "text", text }],
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structuredContent: {
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templates: SCENARIO_TEMPLATES,
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defaultInputs: DEFAULT_INPUTS,
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customProjections: customScenario?.projections,
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customSummary: customScenario?.summary,
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},
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};
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},
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);
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server.registerResource(
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resourceUri,
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resourceUri,
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{ description: "SaaS Scenario Modeler UI" },
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async (): Promise<ReadResourceResult> => {
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const html = await fs.readFile(
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path.join(DIST_DIR, "mcp-app.html"),
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"utf-8",
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);
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return {
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contents: [{ uri: resourceUri, mimeType: "text/html+mcp", text: html }],
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};
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},
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);
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}
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// ============================================================================
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// Express Server
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// ============================================================================
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const app = express();
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app.use(cors());
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app.use(express.json());
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app.post("/mcp", async (req: Request, res: Response) => {
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try {
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const transport = new StreamableHTTPServerTransport({
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sessionIdGenerator: undefined,
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enableJsonResponse: true,
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});
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res.on("close", () => {
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transport.close();
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});
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await server.connect(transport);
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await transport.handleRequest(req, res, req.body);
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} catch (error) {
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console.error("Error handling MCP request:", error);
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if (!res.headersSent) {
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res.status(500).json({
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jsonrpc: "2.0",
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error: { code: -32603, message: "Internal server error" },
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id: null,
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});
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}
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}
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});
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const httpServer = app.listen(PORT, () => {
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console.log(
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`SaaS Scenario Modeler Server listening on http://localhost:${PORT}/mcp`,
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);
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});
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function shutdown() {
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console.log("\nShutting down...");
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httpServer.close(() => {
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console.log("Server closed");
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process.exit(0);
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});
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}
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process.on("SIGINT", shutdown);
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process.on("SIGTERM", shutdown);
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