Docs · Model reference

refinance

Verified · spec v1.0.0

Full specification JSON contract Live demo calculator

Inputs

Field	Type	Valid domain
currentBalance	float	50,000 – 1,500,000
currentRate	float	0.02 – 0.12
currentRemainingMonths	int	12 – 360
newRate	float	0.02 – 0.12
newTermMonths	int	120 – 360
closingCosts	float	0 – 20,000
monthsUntilMove	int	12 – 360

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

Sentinel values

breakEvenMonths = Infinity → never breaks even (monthlySavings ≤ 0; exported as the string "Infinity")

Responses annotate these in a sentinels array with a triggered flag per run.

Live example — generated from the real engine

Request

POST /api/v1/models/refinance
{
  "currentBalance": 775000,
  "currentRate": 0.07,
  "currentRemainingMonths": 186,
  "newRate": 0.07,
  "newTermMonths": 240,
  "closingCosts": 10000,
  "monthsUntilMove": 186
}

Response (chart arrays compacted)

{
  "ok": true,
  "model": "refinance",
  "specVersion": "1.0.0",
  "contractUrl": "/api/v1/models/refinance",
  "specUrl": "/api/v1/models/refinance/spec",
  "inputs": {
    "currentBalance": 775000,
    "currentRate": 0.07,
    "currentRemainingMonths": 186,
    "newRate": 0.07,
    "newTermMonths": 240,
    "closingCosts": 10000,
    "monthsUntilMove": 186
  },
  "outputs": {
    "currentMonthlyPayment": 6839.060350410964,
    "newMonthlyPayment": 6008.566751046266,
    "monthlySavings": 830.4935993646977,
    "breakEvenMonths": 13,
    "netSavingsAtHorizon": 144471.80948183377,
    "worthRefinancing": true
  },
  "sentinels": [
    {
      "field": "breakEvenMonths",
      "value": "Infinity",
      "meaning": "never breaks even (monthlySavings ≤ 0; exported as the string \"Infinity\")",
      "triggered": false
    }
  ],
  "assumptions": [
    "Implements model spec refinance v1.0.0 (dual-implementation verified)."
  ],
  "facts": [],
  "record": {
    "sha256": "15d17ce955bcced4d3f955ef159116cddf8d4d63a14300f6e3287c02e63c9e8f",
    "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.