# HELOC Calculator API

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

Estimate HELOC draw-period and repayment-period payments, interest cost, and combined loan-to-value.

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

- Slug: `heloc-calculator`
- Category: `finance`
- Version: `2026-04-22`
- Credits per successful call: 1
- Starts on: free
- Max payload: 65536 bytes
- Privacy mode: `hash_only`
- Available on: free, starter, pro, business, scale
- Browser tool: https://miniwebtool.com/heloc-calculator/

## Endpoint

`POST https://api.miniwebtool.com/v1/tools/heloc-calculator/run`

## Request body

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `home_value` | `float` | no |  |
| `mortgage_balance` | `float` | no |  |
| `heloc_amount` | `float` | no |  |
| `interest_rate` | `float` | no |  |
| `draw_period` | `str` | no | 5 | 7 | 10 Choices: 5, 7, 10 |
| `repayment_period` | `str` | no | 10 | 15 | 20 Choices: 10, 15, 20 |
| `payment_type` | `str` | no | interest_only | full Choices: interest_only, full |

## Example request

```json
{
  "home_value": 500000,
  "mortgage_balance": 300000,
  "heloc_amount": 50000,
  "interest_rate": 8.5,
  "draw_period": "10",
  "repayment_period": "20",
  "payment_type": "interest_only"
}
```

## cURL

```bash
curl -X POST https://api.miniwebtool.com/v1/tools/heloc-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"home_value":500000,"mortgage_balance":300000,"heloc_amount":50000,"interest_rate":8.5,"draw_period":"10","repayment_period":"20","payment_type":"interest_only"}'
```

## Response envelope

```json
{
  "request_id": "01K...",
  "tool": "heloc-calculator",
  "tool_version": "2026-04-22",
  "credits_used": 1,
  "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 HELOC Calculator API do?

Estimate HELOC draw-period and repayment-period payments, interest cost, and combined loan-to-value. Use it to add this utility without rebuilding formulas, validation, examples, and documentation.

### How much does one call cost?

1 credit per successful call. Failed calls do not bill.

### What parameters are required?

Required fields: (none). Full schema at `https://api.miniwebtool.com/v1/openapi.json`.

### Is this deterministic?

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