# Mortgage Comparison Calculator API

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

Compare two to four fixed-rate mortgages by payment, total interest, total cost, and annual amortization.

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

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

## Endpoint

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

## Request body

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `offers` | `str` | no | 2-4 lines: label, principal, annual_rate_pct, term_years |

## Example request

```json
{
  "offers": "30-year,300000,6.5,30\n15-year,300000,5.9,15"
}
```

## cURL

```bash
curl -X POST https://api.miniwebtool.com/v1/tools/mortgage-comparison-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"offers":"30-year,300000,6.5,30\n15-year,300000,5.9,15"}'
```

## Response envelope

```json
{
  "request_id": "01K...",
  "tool": "mortgage-comparison-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 Mortgage Comparison Calculator API do?

Compare two to four fixed-rate mortgages by payment, total interest, total cost, and annual amortization. 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: (none). Full schema at `https://api.miniwebtool.com/v1/openapi.json`.

### Is this deterministic?

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