Financial planning & wealthtech infrastructure
A financial model API your product can build on
A financial model API returns computed financial answers — retirement projections, mortgage math, tax estimates — over HTTP instead of leaving each product team to rebuild and maintain the formulas. Worthune's API serves 57 models across 8 families, each written to a published, versioned specification, verified against an independently built second implementation on 250 cases, and returned with the government constants it used and a SHA-256 evidence record.
What to look for — whoever you choose
A published contract, not a black box
You should be able to read what a model computes — inputs, valid ranges, formulas, assumptions, and what it deliberately excludes — before you integrate it. If the vendor won't show the spec, you're integrating a guess.
Versioned behavior
Financial rules change every year. The API should pin behavior to a spec version and publish a changelog, so an update never silently moves numbers your product already shipped.
Sourced constants
Every IRS limit, bracket, and factor should trace to a primary source with the date it was last checked. A constant typed in once and never revisited is how calculators quietly go wrong each January.
How Worthune answers it
One POST per computation
Stateless JSON in, deterministic outputs, assumptions, cited constants, and an evidence record out. SDKs on npm and PyPI; MCP for AI assistants.
→ read the quickstart3 models free, no key, no card
The free models run the same specs and the same verification as the paid catalog, so what you evaluate is what you'd buy.
→ see pricingVerification you can re-run
Every model's 250-case file is downloadable for the open models; grade your own engine against ours or read how Concordance testing works.
→ read the methodologyWhere this fits: everything above is one platform — calculators & models, planning software, and unified household management, on the same verified engines and one API. How the numbers are made is public: the methodology.
Common questions
Is there a free financial model API?
Worthune answers 3 full models with no signup, no API key, and no card — over REST, MCP, and an embeddable script tag. They carry the same published specs and verification as the paid catalog of 57 models.
How accurate are the calculations?
Each model is written to a published specification and verified by a second implementation built independently from that spec; the two must agree on 250 deterministic cases at one part in a billion before any release. Every response carries the constants used with their primary sources.
What happens when tax law changes?
Constants live in a sourced, dated registry; when an official source publishes a change, the registry and affected models update with a public spec version bump. Integrations can pin a version so outputs never move silently.
Can I test the math my team already built?
Yes — post your inputs and answers to the grading endpoint and get a pass/fail per case at the same tolerances Worthune's own release checks run, or download the eval datasets into your CI.
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