Jackpot Calculator MCP

Four read-only MCP tools for US lottery prize taxes, cash vs annuity comparisons, equal pool shares and jackpot probabilities. Calculations use a fixed 2026 data snapshot and the same engine as Jackpot Calculator.

Connect to the hosted server

Add this Streamable HTTP URL in a client that supports remote MCP servers:

https://jackpot-calculator-mcp.jiankn.workers.dev/mcp

No API key is required. The public endpoint allows up to 120 requests per minute per IP at the Cloudflare edge; rate limiting is approximate, not a global quota. Connection examples and output units: Jackpot Calculator MCP setup.

Tools

Tool	Required inputs	Output
calculate_lottery_payout	prize, stateCode	Estimated final tax, withholding and cash take-home
compare_lump_sum_annuity	jackpot, cashValue, stateCode	Cash and 30-payment annuity, discounted present value and break-even rate
calculate_pool_share	prize, members, stateCode	One equal owner's share with the whole-ticket withholding threshold
calculate_lottery_odds	game	Distinct-combination jackpot probability; optional expected return with jackpotCash

Money inputs are US dollars. Tax/payout results use integer cents. The odds tool reports money in dollars. Rates and probabilities are fractions, so 0.04 is 4%. Each result states its units, assumptions and related calculator.

Example tool call:

{
  "name": "calculate_lottery_payout",
  "arguments": { "prize": 1000000, "stateCode": "TX", "status": "single" }
}

The bundled 2026 calculation returns an estimated $320,000 final federal tax and $680,000 take-home, separately from $240,000 federal withholding. See the interactive lottery tax calculator to explore other states and filing statuses.

For game-specific cash estimates, select game: "powerball" or game: "megaMillions", provide the known cash prize and compare it with the Powerball payout calculator or Mega Millions tax calculator. For annuities provide both the published cash option and advertised annuity total; the package never guesses the cash option from a fixed percentage.

Run locally from the source or release archive

Node.js 22.12 or newer is required.

git clone https://github.com/jiankn/jackpot-calculator-mcp.git
cd jackpot-calculator-mcp
npm ci
npm test
node src/cli.mjs

The last command starts an MCP stdio server and waits for a client; it is not an interactive CLI prompt. Configure a stdio client with command: "node" and args: ["/absolute/path/to/jackpot-calculator-mcp/src/cli.mjs"]. Only protocol messages go to stdout.

Release archives can also be installed with npm install ./jackpot-calculator-mcp-0.1.0.tgz. An npm registry listing is optional and is not needed for the hosted endpoint.

Calculation boundaries

• US resident taxpayers, same residence and ticket-purchase state; cross-state credits and nonresident alien withholding are not modeled.
• Federal and state tax data is bundled, with original source URLs and dates. No live jackpot lookup, automatic tax update, ticket purchase or ticket check.
• Standard deduction and incremental income tax. State head-of-household uses single-filer state brackets. California assumes a California Lottery prize.
• NYC and Yonkers need an explicit locality with stateCode: "NY". Maryland uses an average county rate; other local income taxes are excluded.
• Annuities use 30 payments, first immediately and then annual payments growing 5%. Tax rules and other income stay constant. Future tax law and investment taxes are not modeled. Annuity methodology and calculator.
• Pool outputs assume all members have the same tax profile. Different people need separate scenarios. Individually rounded fractional-cent shares can differ slightly from the whole prize.
• Odds assume distinct combinations in one drawing. Expected value excludes taxes, Power Play, jackpot sharing and California pari-mutuel payout differences.

Estimates only, not tax or financial advice. Independent of Powerball, Mega Millions, the Multi-State Lottery Association and state lottery operators. Sources and methodology.

Development and releases

npm test checks known payouts, validation, pool withholding, annuity totals, odds and real stdio/HTTP protocol calls. npm run verify:package packs the allowlisted files, installs the archive into a clean directory and invokes the installed server. CI runs both on Windows and Linux.

scripts/sync-engine.mjs is a maintainer-only snapshot step run within the website checkout, before release. It records source hashes in PROVENANCE.md. Standalone users already have the copied files and do not need to run it.

Code: MIT. Compiled data: CC BY 4.0; see LICENSE-DATA.md and the source URLs inside data/. Issues: https://github.com/jiankn/jackpot-calculator-mcp/issues