# 401(k) Calculator API

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

Project 401(k) growth to retirement with employer matching, IRS contribution limits, salary raises, and year-by-year balances.

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

- Slug: `401-k-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/401-k-calculator/

## Endpoint

`POST https://api.miniwebtool.com/v1/tools/401-k-calculator/run`

## Request body

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `current_age` | `int` | no |  |
| `retirement_age` | `int` | no |  |
| `current_salary` | `float` | no |  |
| `current_balance` | `float` | no |  |
| `contribution_pct` | `float` | no | Your contribution as percent of salary |
| `employer_match_pct` | `float` | no | Employer match rate on your contribution |
| `employer_match_limit_pct` | `float` | no | Match applies up to this percent of salary |
| `annual_return_pct` | `float` | no |  |
| `salary_increase_pct` | `float` | no |  |

## Example request

```json
{
  "current_age": 30,
  "retirement_age": 65,
  "current_salary": 75000,
  "contribution_pct": 10,
  "employer_match_pct": 50,
  "employer_match_limit_pct": 6,
  "annual_return_pct": 7
}
```

## cURL

```bash
curl -X POST https://api.miniwebtool.com/v1/tools/401-k-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"current_age":30,"retirement_age":65,"current_salary":75000,"contribution_pct":10,"employer_match_pct":50,"employer_match_limit_pct":6,"annual_return_pct":7}'
```

## Response envelope

```json
{
  "request_id": "01K...",
  "tool": "401-k-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 401(k) Calculator API do?

Project 401(k) growth to retirement with employer matching, IRS contribution limits, salary raises, and year-by-year balances. 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.