# Pendulum Period Calculator API

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

Simple pendulum solver for period, length, gravity, or frequency with planet presets and a large-amplitude correction.

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

- Slug: `pendulum-period-calculator`
- Category: `science`
- 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/pendulum-period-calculator/

## Endpoint

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

## Request body

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `solve_for` | `str` | no | T | L | g | f Choices: T, L, g, f |
| `length` | `float | None` | no | Pendulum length in meters |
| `period` | `float | None` | no | Period in seconds (for solve_for=L or g) |
| `planet` | `str` | no | earth | moon | mars | jupiter | venus | mercury | saturn | custom Choices: earth, moon, mars, jupiter, venus, mercury, saturn, custom |
| `gravity` | `float | None` | no | Custom gravity in m/s^2 (planet=custom) |
| `amplitude_deg` | `float | None` | no | Optional swing amplitude for the large-angle correction |

## Example request

```json
{
  "solve_for": "T",
  "length": 1.0,
  "planet": "earth"
}
```

## cURL

```bash
curl -X POST https://api.miniwebtool.com/v1/tools/pendulum-period-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"solve_for":"T","length":1.0,"planet":"earth"}'
```

## Response envelope

```json
{
  "request_id": "01K...",
  "tool": "pendulum-period-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 Pendulum Period Calculator API do?

Simple pendulum solver for period, length, gravity, or frequency with planet presets and a large-amplitude correction. 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.