Your fintech product needs financial planning models and math. That doesn’t mean you have to build them yourself.
Retirement, mortgages, equity comp, insurance timing — the models every fintech, wealthtech, and insurtech product eventually needs, and none should have to hand-build. Embed Worthune’s verified models and spend your roadmap on the idea only you can build. Your moat was never going to be a calculator; ours is making every calculator provable.
no API key · $0 with attribution · the free tier, in writing
✓ what every response looks like
| breakEvenMonths | 31 |
| monthlySavings | $214.60 |
| specVersion | 1.0.1behavior pinned |
| facts | IRS values used, citedwith sources |
| record.sha256 | 7891f5ea…storable proof |
The math becomes someone else’s job. The proof stays yours to show.
Every fintech roadmap has the same stalled line items: the retirement projector, the payoff planner, the what-if tool. They stall because the math is easy to write, expensive to get right, and worse to maintain. Here’s what happens when you stop owning that problem.
The feature ships this sprint, not next quarter
The engine exists, the edge cases are handled, and the charts come back in the response. Integration is one POST request — or one script tag if you want the whole calculator rendered on your page. What was a two-month build becomes an afternoon of wiring.
→ the 5-minute quickstart“Where does this number come from?” has a real answer
Every model publishes its spec — the formula, the assumptions, what it deliberately leaves out — and every response cites the IRS figures it used, with sources and the version that produced it. When a customer, a reviewer, or your own PM asks, you open a document. You don’t draft an explanation.
→ read the refinance specJanuary stops breaking your product
Contribution limits, brackets, and SSA factors move every year — and stale constants are exactly how calculators quietly go wrong. We watch the primary sources, update the registry, and version every change publicly. Your integration doesn’t move; your numbers stay current.
→ the facts registry, liveYour assistant computes instead of guessing
Language models approximate arithmetic; your users assume it’s exact. Point any MCP-capable assistant at our server and it runs the real model — then cites the spec version in its answer, so the number in the chat is the same number in the spec.
→ MCP setup for Claude & ChatGPTThree steps, no keys, nothing to install
This is genuinely the whole integration.
Pick a model
Browse the catalog and read the spec — inputs, valid ranges, formulas, assumptions. You know exactly what you’re integrating before you write a line.
Call it — or drop it in
POST JSON from your backend, connect the MCP server to your assistant, or embed the finished calculator with a script tag. Same verified engine underneath all three.
Show your work
The response carries outputs, plain-language notes on edge cases, the assumptions, the sourced IRS figures, and an audit hash you can store and re-verify later.
// or the no-backend version — a live verified calculator, on your page:
<div data-worthune-embed="social-security-timing"></div>
<script async src="https://worthune.com/embed.js"></script>Four teams, four first steps
Same engine underneath; a different shortest path for each.
Fintech & wealthtech product teams
Planning features on the roadmap, no appetite to build and re-verify an engine every tax year.
start with the API →AI & agent platforms
Copilots that discuss money can't be trusted to improvise it. Ground them in real computation.
start with MCP →Banks, insurers & advisory firms
Client-facing calculators on your site this quarter — one script tag, no engineering project.
start with embeds →Teams testing financial AI
Verified input-and-expected-output pairs for every model — the answer key your eval harness is missing.
start with the evals →“Verified” is a set of artifacts, not an adjective
Every claim on this page resolves to something you can open and check — that’s the point of the whole system. This table is the map.
| The claim | What enforces it | Check it yourself |
|---|---|---|
| ✓You know what it computes | Every model has a published spec: inputs, units, valid ranges, exact formulas, assumptions, exclusions. Out-of-range inputs are rejected with errors — never silently adjusted. | GET /models/{model}/spec |
| ✓The math is independently confirmed | A second implementation, built from the spec alone, must reproduce the production engine on 250 cases per model, re-checked on every change. Any disagreement stops the release. | the verification method |
| ✓The constants are current and sourced | IRS limits, brackets, and SSA factors live in a registry with the primary source, the tax year, and the date a human verified each value. Responses cite the figures they used. | GET /api/v1/facts |
| ✓It won't change under you | Model behavior changes only with a version bump and a public changelog entry. Responses pin their spec version, so you can hold us to it in your CI. | /models/changelog |
| ✓You can prove where a number came from | Every response includes a SHA-256 record over the model, version, inputs, and outputs. Store it with anything you build on the numbers; recompute it any time to prove they're unaltered. | verify a record (SDK) |
| ✓Even our traction is checkable | We ask you to trust our numbers, so ours are public: aggregate API usage, updated daily, no vanity math. | GET /api/v1/telemetry |
The questions a careful buyer asks
What does it cost?
Everything live today is $0 with attribution — a visible “Powered by Worthune” where end users see results. Fair use is 5,000 runs a month per app, published as a guideline, not enforced as a meter. The promise is in writing, dated, on the pricing page.
What's the catch on “no API keys”?
There isn’t one — no signup means nothing between a developer and a first call. Abuse is handled by a rate backstop (120 requests/minute per IP) that a real integration never touches. Keys arrive only if paid tiers someday need them, and never for what’s free now.
How locked in are we?
You’re not. It’s plain JSON over HTTPS, the response schema is documented, the specs are published, and behavior is pinned by version. If you ever leave, the spec of everything you were computing goes with you — that’s what published contracts mean.
What happens when tax law changes?
We update the registry from the primary source, bump the affected model specs, note it in the changelog, and your integration keeps working — now with current numbers. That maintenance is the product as much as the math is.
Your first verified computation is five minutes away
Paste this into a terminal. No account, no key, no sales call — the fastest way to evaluate us is to use us.
Open the docs →$ curl -s -X POST https://worthune.com/api/v1/models/fire \
-H 'content-type: application/json' \
-d '{"currentAge":34,"currentSavings":120000,
"annualIncome":110000,"annualExpenses":52000,
"savingsRate":0.35,"expectedReturn":0.07,
"withdrawalRate":0.04}'Not building anything? The same verified models power our free personal scenario calculators — retirement, rent vs. buy, career moves, and more. Worthune for Individuals →