For the complete documentation index, see llms.txt.

ESPP Calculator API

finance 2 credits / call v2026-04-22

Estimate ESPP shares, lookback discount, sale proceeds, taxes, and after-tax return.

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

prefer a UI? Open the ESPP Calculator on miniwebtool.com →

Start free — get a key → 1,000 credits · no card · 30 seconds

Endpoint

POST · 2cr

POST https://api.miniwebtool.com/v1/tools/espp-calculator/run

Request body

Field	Type	Req.
`annual_salary`	`float`	—
`contribution_rate_pct`	`float`	—
`offering_months`	`int`	—
`discount_rate_pct`	`float`	—
`start_price`	`float`	—
`purchase_market_price`	`float`	—
`sale_price`	`float`	—
`lookback` yes \| no	`str`	—
`broker_fee`	`float`	—
`ordinary_tax_rate_pct`	`float`	—
`capital_gains_tax_rate_pct`	`float`	—

Cost & access

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

Response envelope

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

Try it

API key *

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

annual_salary (float)

contribution_rate_pct (float)

offering_months (int)

discount_rate_pct (float)

start_price (float)

purchase_market_price (float)

sale_price (float)

lookback (str)

yes | no

broker_fee (float)

ordinary_tax_rate_pct (float)

capital_gains_tax_rate_pct (float)

Response

Response headers

Get your own key

1,000 free calls/mo · no card · key arrives by email

Code examples

curl -X POST https://api.miniwebtool.com/v1/tools/espp-calculator/run \
  -H 'Authorization: Bearer mwt_live_YOUR_KEY' \
  -H 'Content-Type: application/json' \
  -d '{"annual_salary":120000,"contribution_rate_pct":10,"offering_months":6,"discount_rate_pct":15,"start_price":90,"purchase_market_price":100,"sale_price":110,"lookback":"yes"}'

import requests

resp = requests.post(
    'https://api.miniwebtool.com/v1/tools/espp-calculator/run',
    headers={'Authorization': 'Bearer mwt_live_YOUR_KEY'},
    json={'annual_salary': 120000, 'contribution_rate_pct': 10, 'offering_months': 6, 'discount_rate_pct': 15, 'start_price': 90, 'purchase_market_price': 100, 'sale_price': 110, 'lookback': 'yes'},
)
resp.raise_for_status()
data = resp.json()
print(data)

const resp = await fetch(
  'https://api.miniwebtool.com/v1/tools/espp-calculator/run',
  {
    method: 'POST',
    headers: {
      'Authorization': 'Bearer mwt_live_YOUR_KEY',
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({"annual_salary":120000,"contribution_rate_pct":10,"offering_months":6,"discount_rate_pct":15,"start_price":90,"purchase_market_price":100,"sale_price":110,"lookback":"yes"}),
  }
);
const data = await resp.json();
console.log(data);

<?php
$ch = curl_init('https://api.miniwebtool.com/v1/tools/espp-calculator/run');
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer mwt_live_YOUR_KEY',
        'Content-Type: application/json',
    ],
    CURLOPT_POSTFIELDS => json_encode([
    'annual_salary' => 120000,
    'contribution_rate_pct' => 10,
    'offering_months' => 6,
    'discount_rate_pct' => 15,
    'start_price' => 90,
    'purchase_market_price' => 100,
    'sale_price' => 110,
    'lookback' => 'yes'
]),
]);
$resp = curl_exec($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/espp-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 = {
  'annual_salary' => 120000,
  'contribution_rate_pct' => 10,
  'offering_months' => 6,
  'discount_rate_pct' => 15,
  'start_price' => 90,
  'purchase_market_price' => 100,
  'sale_price' => 110,
  'lookback' => 'yes'
}.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{}{
    "annual_salary": 120000,
    "contribution_rate_pct": 10,
    "offering_months": 6,
    "discount_rate_pct": 15,
    "start_price": 90,
    "purchase_market_price": 100,
    "sale_price": 110,
    "lookback": "yes",
  })
  req, _ := http.NewRequest("POST", "https://api.miniwebtool.com/v1/tools/espp-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/espp-calculator/run"))
    .header("Authorization", "Bearer mwt_live_YOUR_KEY")
    .header("Content-Type", "application/json")
    .POST(HttpRequest.BodyPublishers.ofString("{\"annual_salary\":120000,\"contribution_rate_pct\":10,\"offering_months\":6,\"discount_rate_pct\":15,\"start_price\":90,\"purchase_market_price\":100,\"sale_price\":110,\"lookback\":\"yes\"}"))
    .build();

var resp = client.send(req, HttpResponse.BodyHandlers.ofString());
System.out.println(resp.body());

how-to call espp-calculator

Get an API key
Get an API key. Sign up free for a bearer token. 1,000 credits/month, no card.
Assemble the JSON body
Required fields: . See the Request body table above for the full schema.
POST to https://api.miniwebtool.com/v1/tools/espp-calculator/run
Headers: Authorization: Bearer <key> and Content-Type: application/json. Copy-paste snippets in 7 languages are under Code examples.
Parse the response
Envelope: {request_id, tool, tool_version, credits_used, result}. The typed output lives in result.

faq frequently asked

What does the ESPP Calculator API do?+

Estimate ESPP shares, lookback discount, sale proceeds, taxes, and after-tax return. Use it to add this utility without rebuilding formulas, validation, examples, and documentation.

How much does one call to ESPP Calculator cost?+

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

What parameters does the ESPP Calculator API require?+

Required fields: (none). Full schema at /v1/openapi.json.

Is the ESPP 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 ESPP Calculator API?+

Yes. Connect to https://api.miniwebtool.com/v1/mcp over the Model Context Protocol. The agent discovers `espp-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 (espp-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=="espp-calculator")'

see-also related finance tools