Sheet & Flow Landlord Math

io.github.onyxaholguin-cyberPublished by GitHub account onyxaholguin-cyberv1.0.0Updated Oct 24, 2026

Landlord math: rental cash flow, cap rate, DSCR, Airbnb break-even, late fees, lease notices.

VerifiedSTDIODesktop onlyFinance Data & Analytics

Server details

Identifier: io.github.onyxaholguin-cyber/sheet-and-flow-mcp
Transport: STDIO
Runtime: Desktop only
Trust: Verified
Published: Oct 12, 2026

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Overview

AI-generated overview

Offline MCP server that gives an assistant deterministic landlord and rental-property calculators: cash flow, cap rate, DSCR, Airbnb break-even, late fees and…

What you can do: Run year-one rental analysis: NOI, monthly and annual cash flow, cap rate, cash-on-cash, DSCR, gross rent multiplier, break-even occupancy and expense ratio
Compute mortgage principal and interest payments and total interest
Analyze short-term rentals: booked nights, gross revenue, cash flow, RevPAR, break-even occupancy and break-even nightly rate
Calculate rent late fees with grace period, flat, percent and daily components plus a cap, with optional state examples
Work out lease renewal or rent-increase notice dates and the 0-30/31-60/61-90 day window
Compute the 2026 IRS standard mileage deduction
When to use it: Useful when you want an assistant to evaluate a rental or Airbnb deal, size a mortgage payment, check whether a late fee or notice date is right, or apply the 2026 mileage rate, with the same arithmetic every time instead of an estimate.
Requirements: Runs locally over stdio as a local process: a one-click .mcpb bundle for Claude Desktop, or Node.js 18+ pointed at the server entry file, or Docker. No API keys, accounts, environment variables or network access at run time. The plugin manifest installs via npx from a pinned GitHub commit.

Before you install

Results are planning estimates, not legal, tax or investment advice; the late-fee state examples summarize statute text as of October 2026, so verify current law, city rules and the lease before charging a fee. The plugin install path downloads the repository from GitHub at install time. Paid spreadsheet workbooks are offered separately but are not required.

Installation

In SourceWeft

Open Sheet & Flow Landlord Math in the dashboard and add it to a workspace.
Enable the server for the chats that should use its tools.

Desktop only via STDIO. STDIO servers start a local process, so they need the SourceWeft desktop host.

Other MCP clients

Follow the launch instructions in the repository.

README

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.

Tools

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:

json

{  "mcpServers": {    "sheet-and-flow": { "command": "node", "args": ["/path/to/sheet-and-flow-mcp/server/index.js"] }  }}

{  "mcpServers": {    "sheet-and-flow": { "command": "node", "args": ["/path/to/sheet-and-flow-mcp/server/index.js"] }  }}

Docker: docker build -t sheet-and-flow-mcp . then use {"command": "docker", "args": ["run", "-i", "--rm", "sheet-and-flow-mcp"]} in your client config.

It is also listed in the official MCP Registry as io.github.onyxaholguin-cyber/sheet-and-flow-mcp.

Install as an agent plugin (Grok Build, Cursor, Claude Code)

This repo is also a plugin: the MCP server plus three skills that tell the agent when and how to use it.

Skill	Use it for
`landlord-deal-analysis`	"Does this duplex / Airbnb cash flow?", cap rate, cash-on-cash, DSCR, break-even occupancy
`rent-late-fee`	Days late and the late fee, with optional Colorado, New York and Texas limits
`lease-renewal-notice`	When the renewal or rent-increase notice must go out, for one lease or a list

Manifests: .grok-plugin/plugin.json, .cursor-plugin/plugin.json, .claude-plugin/plugin.json; MCP config: .mcp.json.

Privacy and terms: PRIVACY.md (no data collected).

Network and credentials (declared for reviewers): none at run time. The server makes no network calls, reads no files and needs no API key or account. At install time, .mcp.json runs npx -y github:onyxaholguin-cyber/sheet-and-flow-mcp#<full commit sha>, which downloads this repo at that exact pinned commit from GitHub (the package has zero dependencies). test/plugin_check.py fails CI if the pinned commit's server/ differs from the tested code.

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:

json

{ "monthlyCashFlow": -208.64, "keptPerBookedNight": 135.53, "breakEvenOccupancy": 0.6726, "breakEvenNightlyRate": 200.24 }

{ "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

bash

npm test                       # node --test, no install steppython3 test/model.py          # regenerate fixtures from the independent Python modelpython3 scripts/build_mcpb.py  # build dist/*.mcpb and dist/server.json

npm test                       # node --test, no install steppython3 test/model.py          # regenerate fixtures from the independent Python modelpython3 scripts/build_mcpb.py  # build dist/*.mcpb and dist/server.json

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.

Source: README.md at commit 31773ff

Tools

SourceWeft has not started this package in its sandbox yet, so its tools are not known.

Version history

v1.0.0LatestOct 12, 2026

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