Docs · Model reference

529-college-savings

Verified · spec v1.0.0

Full specification JSON contract Live demo calculator

Inputs

Field	Type	Valid domain
childAge	int	0 – 17
collegeStartAge	int	17 – 22
annualTuition	float	10,000 – 100,000
tuitionInflationRate	float	0.02 – 0.1
yearsInCollege	int	2 – 6
currentSaved	float	0 – 200,000
monthlyContribution	float	0 – 5,000
annualReturn529	float	0.03 – 0.12
annualReturnTaxable	float	0.02 – 0.12
incomeTaxRate	float	0.1 – 0.37

collegeStartAge must be at least childAge
annualReturn529 and annualReturnTaxable must stay > 0 (NaN at 0)

All fields required. Out-of-domain values are rejected with per-field errors — never clamped. Unknown fields are rejected.

Live example — generated from the real engine

Request

POST /api/v1/models/529-college-savings
{
  "childAge": 9,
  "collegeStartAge": 20,
  "annualTuition": 55000,
  "tuitionInflationRate": 0.06,
  "yearsInCollege": 4,
  "currentSaved": 100000,
  "monthlyContribution": 2500,
  "annualReturn529": 0.08,
  "annualReturnTaxable": 0.07,
  "incomeTaxRate": 0.24
}

Response (chart arrays compacted)

{
  "ok": true,
  "model": "529-college-savings",
  "specVersion": "1.0.0",
  "contractUrl": "/api/v1/models/529-college-savings",
  "specUrl": "/api/v1/models/529-college-savings/spec",
  "inputs": {
    "childAge": 9,
    "collegeStartAge": 20,
    "annualTuition": 55000,
    "tuitionInflationRate": 0.06,
    "yearsInCollege": 4,
    "currentSaved": 100000,
    "monthlyContribution": 2500,
    "annualReturn529": 0.08,
    "annualReturnTaxable": 0.07,
    "incomeTaxRate": 0.24
  },
  "outputs": {
    "yearsToCollege": 11,
    "projectedTotalCost": 456737.99853390985,
    "projectedBalance529": 759614.8794437214,
    "projectedBalanceTaxable": 639349.1925251021,
    "shortfall": 0,
    "requiredMonthlySavings": 0,
    "taxAdvantage": 120265.68691861932,
    "yearlyData": [
      {
        "year": 9,
        "balance529": 100000,
        "balanceTaxable": 100000,
        "costTarget": 220000
      },
      {
        "year": 10,
        "balance529": 138000,
        "balanceTaxable": 137000,
        "costTarget": 233200
      },
      "… 10 more"
    ]
  },
  "sentinels": [],
  "assumptions": [
    "Implements model spec 529-college-savings v1.0.0 (dual-implementation verified).",
    "collegeStartAge must be at least childAge",
    "annualReturn529 and annualReturnTaxable must stay > 0 (NaN at 0)"
  ],
  "facts": [],
  "record": {
    "sha256": "391ec213747366113acafe178c66a144f466e41fd6175bc79ea8aecb427b53a9",
    "fields": [
      "model",
      "specVersion",
      "inputs",
      "outputs"
    ],
    "howToVerify": "Store this record with any advice or agent output built on these numbers. To verify later: build {model, specVersion, inputs, outputs} from the stored response, serialize as JSON with object keys sorted recursively (no whitespace), and SHA-256 it — a match proves the numbers came from this spec version with these inputs, unaltered."
  },
  "disclaimer": "Illustrative planning model, not financial advice. Outputs follow the published model spec exactly; read the spec for assumptions and exclusions before relying on any number."
}

This example is executed against the production engine when the page builds — it cannot drift from the API's real behavior.