# Car Loan Payoff Calculator API

> For the complete documentation index, see [llms.txt](/llms.txt).

Compare standard and accelerated payoff for a car loan.

Use this endpoint to add the tool to your app, site, workflow, or agent without rebuilding formulas, validation, examples, and docs.

- Slug: `car-loan-payoff-calculator`
- Category: `finance`
- Version: `2026-04-22`
- Credits per successful call: 2
- Starts on: starter
- Max payload: 65536 bytes
- Privacy mode: `hash_only`
- Available on: starter, pro, business, scale
- Browser tool: https://miniwebtool.com/car-loan-payoff-calculator/

## Endpoint

`POST https://api.miniwebtool.com/v1/tools/car-loan-payoff-calculator/run`

## Request body

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `loan_balance` | `float` | yes |  |
| `interest_rate_percent` | `float` | yes |  |
| `monthly_payment` | `float` | yes |  |
| `extra_monthly` | `float` | no |  |
| `one_time_payment` | `float` | no |  |
| `one_time_month` | `int` | no |  |
| `precision` | `int` | no |  |

## Example request

```json
{
  "loan_balance": 18000,
  "interest_rate_percent": 6.5,
  "monthly_payment": 400,
  "extra_monthly": 50
}
```

## cURL

```bash
curl -X POST https://api.miniwebtool.com/v1/tools/car-loan-payoff-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"loan_balance":18000,"interest_rate_percent":6.5,"monthly_payment":400,"extra_monthly":50}'
```

## Response envelope

```json
{
  "request_id": "01K...",
  "tool": "car-loan-payoff-calculator",
  "tool_version": "2026-04-22",
  "credits_used": 2,
  "result": {}
}
```

## Errors

Errors are RFC 7807 `application/problem+json`. Branch on `code`, not `title`.

## MCP

Agents can discover and call this tool through `https://api.miniwebtool.com/mcp` or `https://api.miniwebtool.com/v1/mcp` using MCP `tools/list` and `tools/call`.

## Frequently asked

### What does the Car Loan Payoff Calculator API do?

Compare standard and accelerated payoff for a car loan. Use it to add this utility without rebuilding formulas, validation, examples, and documentation.

### How much does one call cost?

2 credits per successful call. Failed calls do not bill.

### What parameters are required?

Required fields: loan_balance, interest_rate_percent, monthly_payment. Full schema at `https://api.miniwebtool.com/v1/openapi.json`.

### Is this deterministic?

Yes. Same input, same output. Tool version: 2026-04-22.