Inputs
| Field | Type | Valid domain |
|---|---|---|
| loanAmount | float | 1,000 – 2,000,000 |
| annualRateA | float | 0 – 0.3 |
| termMonthsA | int | 6 – 480 |
| feesA | float | 0 – 20,000 |
| annualRateB | float | 0 – 0.3 |
| termMonthsB | int | 6 – 480 |
| feesB | float | 0 – 20,000 |
- Costs are lifetime nominal dollars (interest + fees), undiscounted. Comparing offers with different terms ignores time value and payment duration — a longer loan's lower nominal total can still be worse in present-value terms.
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/loan-comparison
{
"loanAmount": 1001000,
"annualRateA": 0.15,
"termMonthsA": 243,
"feesA": 10000,
"annualRateB": 0.15,
"termMonthsB": 243,
"feesB": 10000
}Response (chart arrays compacted)
{
"ok": true,
"model": "loan-comparison",
"specVersion": "1.0.0",
"contractUrl": "/api/v1/models/loan-comparison",
"specUrl": "/api/v1/models/loan-comparison/spec",
"inputs": {
"loanAmount": 1001000,
"annualRateA": 0.15,
"termMonthsA": 243,
"feesA": 10000,
"annualRateB": 0.15,
"termMonthsB": 243,
"feesB": 10000
},
"outputs": {
"monthlyPaymentA": 13155.350016081906,
"monthlyPaymentB": 13155.350016081906,
"totalInterestA": 2195750.053907903,
"totalInterestB": 2195750.053907903,
"totalCostA": 2205750.053907903,
"totalCostB": 2205750.053907903,
"monthlyDelta": 0,
"cheaperOption": "tie",
"lifetimeSavings": 0
},
"sentinels": [],
"assumptions": [
"Implements model spec loan-comparison v1.0.0 (dual-implementation verified).",
"Costs are lifetime nominal dollars (interest + fees), undiscounted. Comparing offers with different terms ignores time value and payment duration — a longer loan's lower nominal total can still be worse in present-value terms."
],
"facts": [],
"record": {
"sha256": "fe6f88e94227f796b3a94b7f04e6c9962cee2decefe6f5604464a3cab7ac6b60",
"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.