For developers & AI assistants
Financial models that show their work
Every model here tells you what it takes in, what it computes, what it assumes, and what it leaves out — before you run it. A second, independent implementation has to reproduce the engine exactly before anything ships, every IRS and SSA constant is traced to its source, and when a model changes, the changelog tells you.
Watch the film — Two Implementations or It Doesn’t Ship, 3½ minutes
Use the models
MCP server (AI assistants): https://worthune.com/api/mcp/mcp — your agent lists the catalog, reads the contract, runs the model, and can check a claim before stating it; the household tools create, project, decide, and verify a stored household end to end. Twenty tools, six keyless, in the official MCP registry as com.worthune/models. The three sample models answer without a key; a paid key, sent once as a bearer header, opens the rest.
REST API: GET /api/v1/models lists the catalog; every model serves its contract, its full spec, and a POST endpoint that validates before it computes — out-of-range requests get an error, not a quietly adjusted answer. Responses carry their spec version, assumptions, and sourced constants.
Aggregate usage is public at /api/v1/telemetry — counters only, never personal data.
The catalog, by the decision it answers
61 models in 9 families, each written to a versioned spec and re-checked against a second independent implementation on every change. Spec links are public for the three sample models — emergency-fund, relocation, and side-business — and open with a key for the rest; every model’s input contract is public either way.
Housing & mortgages
rent vs. buy, refinance break-even, down payment, points, PMI, ARM vs. fixedRetirement & withdrawal
FIRE, Roth vs. traditional, conversion ladders, RMDs, Social Security timingEquity comp & taxes
newAMT on ISO exercise, QSBS, 83(b), wash sales, RSUs, ESPP, capital gains, income cliffs, state income taxLongevity, insurance & care
newlongevity horizon, annuity payout, life-insurance need, long-term care, estatesEstate & legacy
newestate-tax exposure, step-up vs. gift-now basis, the inherited-IRA 10-year rule, QCDs, 529 superfundingDebt & loans
payoff strategies, student loans, auto loans, loan comparison, card minimumsLife decisions & household
relocation, a child, a wedding, a sabbatical, one income, divorce, windfalls| Model | Spec | Try it | Contract |
|---|---|---|---|
| relocationfree | v1.0.0 | calculator | JSON |
| having-a-child | v1.1.0 | calculator | JSON |
| wedding | v1.1.0 | calculator | JSON |
| divorce | v1.2.0 | calculator | JSON |
| sabbatical | v1.0.0 | calculator | JSON |
| one-income | v1.0.0 | calculator | JSON |
| renovation | v1.1.0 | calculator | JSON |
| windfall | v1.0.1 | calculator | JSON |
| salary-jump | v1.0.1 | calculator | JSON |
| emergency-fundfree | v1.0.0 | calculator | JSON |
Education
529 savings, private school| Model | Spec | Try it | Contract |
|---|---|---|---|
| 529-college-savings | v1.0.0 | calculator | JSON |
| private-school | v1.2.0 | calculator | JSON |
Model changes are never silent — the full version history is at /models/changelog. Before any change ships, an independent implementation written from the spec alone has to agree with the engine’s results, across 250 open test cases per model checked against textbook values — how Concordance testing works. Models are illustrative planning tools, not financial advice.