# Compound Interest — MCP tool `findutils:compound_interest`

Compute compound interest growth. Supports any compound frequency (monthly, quarterly, annual) plus optional fixed monthly contributions. Returns final balance, total contributions, total interest, and a year-by-year balance series.

- Category: finance
- MCP server: https://mcp.findutils.com/ (Streamable HTTP, no API keys, 120 req/min per IP)
- REST endpoint: POST https://api.findutils.com/api/tools/compound-interest/execute (no API keys, 60 req/min per IP)
- Reference page: https://findutils.com/mcp/compound-interest/
- Same tool on the other surface: https://findutils.com/api/compound-interest/

## Connect

```bash
claude mcp add findutils --transport http https://mcp.findutils.com/
```

Claude Desktop (`claude_desktop_config.json`):

```json
{
  "mcpServers": {
    "findutils": {
      "url": "https://mcp.findutils.com/"
    }
  }
}
```

## Call the tool (verified example)

```bash
curl -X POST https://mcp.findutils.com/ \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
      "name": "compound_interest",
      "arguments": {
        "principal": 1000,
        "annual_rate": 0.05,
        "years": 5
      }
    }
  }'
```

## Input schema

| Argument | Type | Required | Description |
|---|---|---|---|
| `principal` | number | yes | Starting principal (in any currency). |
| `annual_rate` | number | yes | Annual interest rate as a decimal (0.07 = 7%). |
| `years` | number | yes | Investment duration in years. |
| `compounds_per_year` | integer | no | Compound periods per year. Default: 12 (monthly). |
| `monthly_contribution` | number | no | Optional fixed monthly contribution. Default: 0. |

Example arguments (verified):

```json
{
  "principal": 1000,
  "annual_rate": 0.05,
  "years": 5
}
```

## Also a REST endpoint

```bash
curl -X POST https://api.findutils.com/api/tools/compound-interest/execute \
  -H "Content-Type: application/json" \
  -d '{
    "principal": 1000,
    "annual_rate": 0.05,
    "years": 5
  }'

# Parameter schema
curl https://api.findutils.com/api/tools/compound-interest
```

Full REST reference: https://findutils.com/api/compound-interest/ · OpenAPI 3.1 spec: https://findutils.com/api/openapi.json

---
Full catalog: POST https://mcp.findutils.com/ with method `tools/list` · https://findutils.com/mcp/ · https://findutils.com/llms.txt