Inputs
| Field | Type | Valid domain |
|---|---|---|
| loanAmount | float | 10,000 – 2,000,000 |
| termMonths | int | 60 – 480 |
| baseRate | float | 0.005 – 0.15 |
| reducedRate | float | 0.001 – 0.15 |
| pointsPct | float | 0 – 0.05 |
All fields required. Out-of-domain values are rejected with per-field errors — never clamped. Unknown fields are rejected.
Sentinel values
breakEvenMonths=Infinity→ paid points never break even (monthlySavings ≤ 0, including reducedRate ≥ baseRate); free points that save nothing break even at 0
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/points-break-even
{
"loanAmount": 1005000,
"termMonths": 270,
"baseRate": 0.08,
"reducedRate": 0.08,
"pointsPct": 0.03
}Response (chart arrays compacted)
{
"ok": true,
"model": "points-break-even",
"specVersion": "1.0.0",
"contractUrl": "/api/v1/models/points-break-even",
"specUrl": "/api/v1/models/points-break-even/spec",
"inputs": {
"loanAmount": 1005000,
"termMonths": 270,
"baseRate": 0.08,
"reducedRate": 0.08,
"pointsPct": 0.03
},
"outputs": {
"pointsCost": 30150,
"basePayment": 8036.360337286342,
"reducedPayment": 8036.360337286342,
"monthlySavings": 0,
"breakEvenMonths": "Infinity",
"worthIt": false,
"lifetimeSavings": -30150
},
"sentinels": [
{
"field": "breakEvenMonths",
"value": "Infinity",
"meaning": "paid points never break even (monthlySavings ≤ 0, including reducedRate ≥ baseRate); free points that save nothing break even at 0",
"triggered": true
}
],
"assumptions": [
"Implements model spec points-break-even v1.0.0 (dual-implementation verified)."
],
"facts": [],
"record": {
"sha256": "fb26b6d072e92fe04caa8c1da6178e0cec95bf2d10ad1d628230f12ed8b0f459",
"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.