# Finance Calculators – Compound Interest

> Finance Calculators – Compound Interest is a paid API for AI agents from finance-calculators.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Calculates the future value of savings with compound interest and optional monthly contributions, returning year-by-year balance, total contributions, and interest earned.

## Facts

- Endpoint: GET https://finance-calculators.x402tookit.com/compound-interest?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/finance-calculators-compound-interest-be4bad1a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_HFuhNbCAxbAwRd-7GHzLp

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability finance-calculators-compound-interest-be4bad1a
```

Example prompt: How much will my $5,000 savings grow to in 10 years at 6% annual interest compounded monthly, if I also add $150 each month? Show me the year-by-year breakdown.

## When to prefer this

Choose this endpoint when you need a precise mathematical projection of savings growth over time with optional recurring contributions and configurable compounding frequency. It returns a full year-by-year breakdown, making it ideal for planning dashboards, retirement projections, or educational financial tools. Prefer it over generic calculators when you need the byYear series or the contributions-vs-interest breakdown.

## Known failure modes

- Missing required parameters (principal, annual_rate_pct, or years) returns an error
- Negative or zero values for principal or years may produce undefined or error responses
- Extremely large year values or rates may produce impractical outputs
- Non-numeric query parameters result in validation errors

## How this service works

Future value of savings with compounding and monthly contributions: balance, contributions, interest earned, by year.

## Output

Returns a structured object with: the final future value, total amount contributed, total interest earned, a multiple-of-contributions ratio, and a byYear array showing the running balance for each year of the investment horizon.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "principal",
      "annual_rate_pct",
      "years"
     ],
     "properties": {
      "years": {
       "type": "number",
       "description": "Years"
      },
      "principal": {
       "type": "number",
       "description": "Starting amount"
      },
      "annual_rate_pct": {
       "type": "number",
       "description": "Annual rate in percent"
      },
      "compounds_per_year": {
       "type": "integer",
       "description": "Default 12"
      },
      "monthly_contribution": {
       "type": "number",
       "description": "Added each month, default 0"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "byYear": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "object",
        "properties": {
         "year": {
          "type": [
           "null",
           "number"
          ]
         },
         "balance": {
          "type": [
           "null",
           "number"
          ]
         }
        }
       }
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "futureValue": {
       "type": [
    
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/finance-calculators-compound-interest-be4bad1a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from finance-calculators.x402tookit.com](https://www.zero.xyz/host/finance-calculators.x402tookit.com/llms.txt)