Guides
How it works
How the app, the calc engine, and the MCP server fit together — and where your data lives.
CostPad is one calc engine with three faces: the visual app, the headless MCP server, and your AI assistant. They all read the same model and produce the same numbers.
One engine, one model
- Your model — COGS items, pricing tiers, user mix, add-ons, and operating scalars.
- The calc engine — one shared engine turns the model into economics: blended ARPU, COGS per user, payment fees, free-tier burn, scale, and growth. The app and the MCP server run the same engine, so the numbers always match.
- The surfaces — the app renders the economics as panels; the MCP server exposes them as tools, prompts, and resources for an assistant.
Where your data lives
Your model is stored locally — in your browser or desktop app storage. No accounts, no telemetry. The optional Cloud plan adds cross-device sync and multiple products; everything else stays on your machine. When the desktop app is running, the MCP server can bridge to it locally so an assistant works on your real numbers.
Next: the core concepts behind the panels.