# FastX402 Loan Payment Calculator

> FastX402 Loan Payment Calculator is a paid API for AI agents from fastx402.tools, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-27).

Calculates monthly mortgage/loan payment, total interest, and total amount paid given principal, annual rate, and term in months

## Facts

- Endpoint: GET https://fastx402.tools/loan-payment?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-27
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastx402-loan-payment-calculator-f7a963d5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_R5KGQdVFZqLZoqcWXZCEN

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 fastx402-loan-payment-calculator-f7a963d5
```

Example prompt: What would my monthly payment be on a $250,000 mortgage at 4.5% annual interest paid over 30 years (360 months), and how much total interest would I end up paying?

## When to prefer this

Use this endpoint when you need a quick, accurate fixed-rate loan amortization calculation — monthly payment, total interest, and total paid — without setting up an account or API key. Ideal for AI agents that need on-demand financial computation for mortgage, auto, or personal loan scenarios, paying only $0.002 per call in USDC via x402 on Base or Solana.

## Known failure modes

- Missing required query parameters (principal, annual_rate_percent, months) returns an error
- Non-numeric or negative values for principal/rate/months may return an error or nonsensical result
- Annual rate of 0% may cause division edge cases
- Extremely large principals or very short terms may return unexpected values
- Payment via x402 fails if wallet has insufficient USDC balance

## How this service works

200 pay-per-call tools for AI agents, from $0.001 per request in USDC on Base or Solana with x402. No account, no API key.

## Output

Returns a JSON object with: monthly_payment (fixed monthly installment), total_paid (sum of all payments over the loan term), total_interest (total interest cost above principal), plus echoes of the input values: principal, annual_rate_percent, and months.

## 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_percent",
      "months"
     ],
     "properties": {
      "months": {
       "type": "string",
       "description": "Number of monthly payments, e.g. 360"
      },
      "principal": {
       "type": "string",
       "description": "Loan amount, e.g. 250000"
      },
      "annual_rate_percent": {
       "type": "string",
       "description": "Yearly interest rate in percent, e.g. 4.5"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "months": {
       "type": "integer"
      },
      "principal": {
       "type": "integer"
      },
      "total_paid": {
       "type": "number"
      },
      "total_interest": {
       "type": "number"
      },
      "monthly_payment": {
       "type": "number"
      },
      "annual_rate_percent": {
       "type": "number"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "months": 360,
  "principal": 250000,
  "total_paid": 456015.6,
  "total_interest": 206015.6,
  "monthly_payment": 1266.71,
  "annual_rate_percent": 4.5
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastx402-loan-payment-calculator-f7a963d5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from fastx402.tools](https://www.zero.xyz/host/fastx402.tools/llms.txt)