Sheet & Flow Landlord Math (MCP server)
Landlord and rental-property calculators as Model Context Protocol tools, so Claude, Cursor, VS Code or any MCP client does the math the same way every time instead of estimating it.
- Offline and deterministic. No network calls, no API keys, no data leaves your computer.
- No dependencies. Plain Node.js (18+), about 380 lines you can read.
- Tested. 552 randomized cases against an independent Python model, and the worked examples from the Sheet & Flow tutorials, on Node 18, 20 and 22 in CI. The rental math was also cross-checked against spreadsheet-recalculated (LibreOffice) deals before release.
| Tool | What it answers |
|---|
rental_property_analysis | Year-one NOI, monthly and annual cash flow, cap rate, cash-on-cash, DSCR, gross rent multiplier, break-even occupancy, expense ratio |
mortgage_payment | Monthly principal and interest, total interest |
short_term_rental_analysis | Airbnb/VRBO booked nights, stays, gross revenue, cash flow, RevPAR, what each booked night is worth, break-even occupancy and break-even nightly rate |
rent_late_fee | Days late and the late fee: grace period, flat + percent + daily fees, a cap; optional Colorado / New York / Texas examples |
lease_renewal_notice | Date the renewal or rent-increase notice must go out, 0-30/31-60/61-90 day window, status, next lease end |
irs_mileage_deduction_2026 | 2026 IRS standard mileage deduction (business 72.5¢ Jan–Jun, 76¢ Jul–Dec) |
Percentages are fractions (0.25 = 25%). Dates are YYYY-MM-DD. A percentage passed as 7 instead of 0.07 is rejected with a clear message rather than silently computed.
Install
Claude Desktop (one click): download sheet-and-flow-mcp-<version>.mcpb from the latest release and open it.
Any MCP client (stdio): clone the repo and point your client at server/index.js:
{
"mcpServers": {
"sheet-and-flow": { "command": "node", "args": ["/path/to/sheet-and-flow-mcp/server/index.js"] }
}
}
It is also listed in the official MCP Registry as io.github.onyxaholguin-cyber/sheet-and-flow-mcp.
Example
Ask: "Airbnb deal: $350,000, 25% down at 7%, $185 a night, 62% occupancy, 14 blocked nights, 3.2-night stays, $95 cleaning fee, $85 cleaning cost, 15.5% host fee, 9% maintenance, $920/month fixed costs, $10,500 closing, $25,000 furnishing. Does it cash flow?"
short_term_rental_analysis returns, among other fields:
{ "monthlyCashFlow": -208.64, "keptPerBookedNight": 135.53, "breakEvenOccupancy": 0.6726, "breakEvenNightlyRate": 200.24 }
So the deal loses about $209 a month as quoted; it needs 67.3% occupancy at $185, or $200.24 a night at 62%. The same example is worked step by step in the short-term rental calculator tutorial.
How the math works
Every formula is explained in a free tutorial:
Prefer a spreadsheet?
The same math comes as finished Excel / Google Sheets workbooks from Sheet & Flow (paid; this server is free and MIT-licensed and doesn't need them):
Short-Term Rental Deal Analyzer ·
Rental Property Deal Analyzer ·
Landlord Tenant Toolkit ·
Lease Renewal Tracker ·
Freelancer Mileage Log ·
Free Rental Cash Flow Calculator
Development
npm test
python3 test/model.py
python3 scripts/build_mcpb.py
Releases: pushing a v* tag runs the tests, builds the .mcpb, attaches it to a GitHub release and publishes server.json to the MCP Registry with GitHub OIDC (no stored tokens).
Disclaimer
Estimates for planning only. Not legal, tax or investment advice. The late-fee state examples are a summary of statute text as of October 2026; check current law, city rules and your lease before charging a fee.
MIT License © Sheet & Flow