For the complete documentation index, see llms.txt.

Credit Card Interest Calculator API

finance 2 credits / call v2026-04-22

Estimate credit card payoff time, interest cost, and payment strategy savings.

One POST adds Credit Card Interest Calculator to your app, site, workflow, or agent — formula, validation, edge cases, and docs already handled.

prefer a UI? Open the Credit Card Interest Calculator on miniwebtool.com →

Start Starter → Requires Starter+ · $29/mo
Starts on Starter
Free keys can view docs and examples, but calls to this endpoint require Starter or higher.
Start Starter →

Endpoint

POST · 2cr
POST https://api.miniwebtool.com/v1/tools/credit-card-interest-calculator/run

Request body

Field Type Req.
balance float
apr_percent float
min_percent float
min_amount float
fixed_payment float | None
precision int

Cost & access

  • 2 credits per successful call — failed calls refund.
  • Starts on: Starter or higher.
  • Max payload: 65536 bytes.
  • Privacy mode: hash_only
  • Available on: starter, pro, business, scale

Response envelope

{
  "request_id": "01K...",
  "tool": "credit-card-interest-calculator",
  "tool_version": "2026-04-22",
  "credits_used": 2,
  "result": { ... }
}

Try it

Stored only in this browser tab. Playground test key is prefilled and only works on this page. Get a live key →

Code examples

curl -X POST https://api.miniwebtool.com/v1/tools/credit-card-interest-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"balance":5000,"apr_percent":19.99,"min_percent":2,"min_amount":25,"fixed_payment":200}'
import requests

resp = requests.post(
    'https://api.miniwebtool.com/v1/tools/credit-card-interest-calculator/run',
    headers={'Authorization': 'Bearer mwt_live_YOUR_KEY'},
    json={'balance': 5000, 'apr_percent': 19.99, 'min_percent': 2, 'min_amount': 25, 'fixed_payment': 200},
)
resp.raise_for_status()
print(resp.json())
const resp = await fetch(
  'https://api.miniwebtool.com/v1/tools/credit-card-interest-calculator/run',
  {
    method: 'POST',
    headers: {
      'Authorization': 'Bearer mwt_live_YOUR_KEY',
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({"balance":5000,"apr_percent":19.99,"min_percent":2,"min_amount":25,"fixed_payment":200}),
  }
);
const data = await resp.json();
console.log(data);
<?php
$ch = curl_init('https://api.miniwebtool.com/v1/tools/credit-card-interest-calculator/run');
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer mwt_live_YOUR_KEY',
        'Content-Type: application/json',
    ],
    CURLOPT_POSTFIELDS => json_encode([
    'balance' => 5000,
    'apr_percent' => 19.99,
    'min_percent' => 2,
    'min_amount' => 25,
    'fixed_payment' => 200
]),
]);
$resp = curl_exec($ch);
curl_close($ch);
print_r(json_decode($resp, true));
require 'net/http'
require 'json'
require 'uri'

uri = URI('https://api.miniwebtool.com/v1/tools/credit-card-interest-calculator/run')
http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = (uri.scheme == 'https')

req = Net::HTTP::Post.new(uri)
req['Authorization'] = 'Bearer mwt_live_YOUR_KEY'
req['Content-Type'] = 'application/json'
req.body = {
  'balance' => 5000,
  'apr_percent' => 19.99,
  'min_percent' => 2,
  'min_amount' => 25,
  'fixed_payment' => 200
}.to_json

resp = http.request(req)
puts JSON.parse(resp.body).inspect
package main

import (
  "bytes"
  "encoding/json"
  "fmt"
  "io"
  "net/http"
)

func main() {
  body, _ := json.Marshal(map[string]interface{}{
    "balance": 5000,
    "apr_percent": 19.99,
    "min_percent": 2,
    "min_amount": 25,
    "fixed_payment": 200,
  })
  req, _ := http.NewRequest("POST", "https://api.miniwebtool.com/v1/tools/credit-card-interest-calculator/run", bytes.NewReader(body))
  req.Header.Set("Authorization", "Bearer mwt_live_YOUR_KEY")
  req.Header.Set("Content-Type", "application/json")

  resp, err := http.DefaultClient.Do(req)
  if err != nil { panic(err) }
  defer resp.Body.Close()
  out, _ := io.ReadAll(resp.Body)
  fmt.Println(string(out))
}
import java.net.URI;
import java.net.http.*;

var client = HttpClient.newHttpClient();
var req = HttpRequest.newBuilder()
    .uri(URI.create("https://api.miniwebtool.com/v1/tools/credit-card-interest-calculator/run"))
    .header("Authorization", "Bearer mwt_live_YOUR_KEY")
    .header("Content-Type", "application/json")
    .POST(HttpRequest.BodyPublishers.ofString("{\"balance\":5000,\"apr_percent\":19.99,\"min_percent\":2,\"min_amount\":25,\"fixed_payment\":200}"))
    .build();

var resp = client.send(req, HttpResponse.BodyHandlers.ofString());
System.out.println(resp.body());
how-to call credit-card-interest-calculator
  1. Get an API key
    Get an API key. Choose the Starter plan or higher to receive a bearer token with access to this endpoint.
  2. Assemble the JSON body
    Required fields: balance, apr_percent, . See the Request body table above for the full schema.
  3. POST to https://api.miniwebtool.com/v1/tools/credit-card-interest-calculator/run
    Headers: Authorization: Bearer <key> and Content-Type: application/json. Copy-paste snippets in 7 languages are under Code examples.
  4. Parse the response
    Envelope: {request_id, tool, tool_version, credits_used, result}. The typed output lives in result.
faq frequently asked
What does the Credit Card Interest Calculator API do?+

Estimate credit card payoff time, interest cost, and payment strategy savings. Use it to add this utility without rebuilding formulas, validation, examples, and documentation.

How much does one call to Credit Card Interest Calculator cost?+

2 credits per successful call. Failed calls (validation errors, 5xx) don't bill.

What parameters does the Credit Card Interest Calculator API require?+

Required fields: balance, apr_percent. Full schema at /v1/openapi.json.

Is the Credit Card Interest Calculator API deterministic?+

Yes — same input, same output, forever. Tool version 2026-04-22; output shape is stable within a major version.

Can an AI agent call the Credit Card Interest Calculator API?+

Yes. Connect to https://api.miniwebtool.com/v1/mcp over the Model Context Protocol. The agent discovers `credit-card-interest-calculator` with its JSON Schema automatically, so the model can plan while MiniWebtool handles the exact tool result.

What format does the API return?+

JSON with a stable envelope: `{request_id, tool, tool_version, credits_used, result}`. Errors are RFC 7807 `application/problem+json`.

mcp use from an AI agent

Every endpoint on this site is also exposed via the Model Context Protocol at https://api.miniwebtool.com/v1/mcp. Claude, Cursor, and any MCP-capable agent can discover this tool (credit-card-interest-calculator) and its JSON Schema automatically — no client codegen.

# List tools the agent can call
curl -s https://api.miniwebtool.com/v1/mcp \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' \
 | jq '.result.tools[] | select(.name=="credit-card-interest-calculator")'
see-also related finance tools