# Simple and Compound Interest Calculator

> Simple and Compound Interest Calculator is a paid API for AI agents from finance.openverbs.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-15).

Calculates the final amount after growing a principal by simple or compound interest over a specified number of years, with configurable compounding frequency.

## Facts

- Endpoint: POST https://finance.openverbs.com/v1/interest
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/simple-and-compound-interest-calculator-ea8f8e87
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ei27pMIzSBo32ftqYHfYr

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 simple-and-compound-interest-calculator-ea8f8e87 -d '<json body>'
```

Example prompt: If I invest $25,000 at an annual rate of 6.5% compounded monthly for 10 years, how much will it grow to?

## When to prefer this

Use this endpoint when you need a straightforward interest growth calculation given a fixed annual rate, principal, and time period — either simple or compound. Prefer this over future value or NPV endpoints when you are not dealing with recurring cash flows or annuities, just a lump sum growing at a fixed rate. Ideal for savings projections, loan interest estimates, and basic investment modeling.

## Known failure modes

- Missing required fields (principal, annualRatePercent, years) returns a validation error
- Years or rate exceeding maximum bounds (1000 years, 1000% rate) returns a range error
- Invalid method enum value (not 'simple' or 'compound') returns a schema validation error
- compoundsPerYear outside 1–365 range returns a validation error
- Non-numeric input for numeric fields returns a type error

## How this service works

Grow a principal by simple or compound interest over a number of years. Compound interest uses compoundsPerYear compounding periods (default 12, monthly).

## Output

Returns the grown principal amount after applying simple or compound interest over the specified period, reflecting the starting principal, annual rate, number of years, and compounding frequency.

## Request schema (JSON Schema)

```json
{
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "type": "object",
 "properties": {
  "input": {
   "type": "object",
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "type": "string",
     "enum": [
      "POST"
     ]
    },
    "bodyType": {
     "type": "string",
     "enum": [
      "json",
      "form-data",
      "text"
     ]
    },
    "body": {
     "type": "object",
     "properties": {
      "principal": {
       "type": "number",
       "minimum": 0,
       "maximum": 1000000000000000,
       "description": "Starting principal."
      },
      "annualRatePercent": {
       "type": "number",
       "minimum": 0,
       "maximum": 1000,
       "description": "Annual interest rate as a percentage."
      },
      "years": {
       "type": "number",
       "minimum": 0,
       "maximum": 1000,
       "description": "Number of years."
      },
      "method": {
       "type": "string",
       "enum": [
        "simple",
        "compound"
       ],
       "description": "Interest method. Default compound."
      },
      "compoundsPerYear": {
       "type": "integer",
       "minimum": 1,
       "maximum": 365,
       "description": "Compounding periods per year (compound only). Default 12."
      }
     },
     "required": [
      "principal",
      "annualRatePercent",
      "years"
     ],
     "additionalProperties": false
    }
   },
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "additionalProperties": false
  }
 },
 "required": [
  "input"
 ]
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/simple-and-compound-interest-calculator-ea8f8e87/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from finance.openverbs.com](https://www.zero.xyz/host/finance.openverbs.com/llms.txt)