Free calculator API and MCP server
Use the kWhmate, Korea Survival Kit and 계산메이트 calculators from your own code, a ChatGPT GPT or any MCP client. Free, read-only, no key. Every result includes the official reference date and source, and the page URL.
Endpoints
| Index | GET https://kwhmate.com/api/v1/ |
| OpenAPI 3.1 | GET https://kwhmate.com/api/v1/openapi.json |
| Run a calculator | GET https://kwhmate.com/api/v1/<id>?… or POST with a JSON body |
| MCP server | POST https://kwhmate.com/api/mcp (Streamable HTTP, JSON responses) |
Example: https://kwhmate.com/api/v1/kr-electricity?kwh=300 returns the bill, the tier breakdown, reference (date and official source) and page.
Calculators
| id | What it calculates |
|---|---|
kr-electricity | Korea household electricity bill (KEPCO residential low-voltage, progressive tiers) |
kr-led-savings | Korea LED replacement savings (household tiers or shop unit price) |
tw-electricity | Taiwan electricity bill (Taipower residential progressive rates) |
tw-led-savings | Taiwan LED replacement savings (Taipower non-summer, monthly brackets) |
ph-meralco | Philippines Meralco bill (this month's residential rate) |
ph-led-savings | Philippines LED replacement savings (Meralco rates) |
jp-electricity | Japan electricity bill (TEPCO Juryo Dento B) |
jp-led-savings | Japan LED replacement savings (TEPCO Juryo Dento B, 30 A) |
seoul-taxi | Seoul taxi fare (regular mid-size taxi meter estimate) |
busan-taxi | Busan taxi fare (regular mid-size taxi meter estimate) |
korea-tax-refund | Korea tourist tax (VAT) refund estimate |
suneung-score | 수능 표준점수·등급 (Korean CSAT standard score and grade) |
naesin-grade | 내신 등급 (Korean high-school class rank → grade, 5- or 9-grade system) |
gpa-converter | 학점 비례 환산 (GPA scale conversion 4.5 / 4.3 / 4.0) |
student-loan | 학자금대출 상환 (Korean student loan: standard repayment or income-contingent ICL) |
education-tax-credit | 교육비 세액공제 (Korean education expense tax credit, 2026 spending) |
gap-investment | 갭투자 실투자금 (Korean "gap" investment: acquisition tax, brokerage, cash needed) |
report-reward | 신고 포상금·보상금 (Korean whistleblower rewards: tax evasion, hidden assets, card refusal, public interest, corruption) |
travel-budget | 국내 여행 예산 (Korea domestic trip budget: transport, stay, food, admission ranges) |
Parameters, limits and defaults for each one are in the index (/api/v1/) and the OpenAPI file. Lists go in as comma-separated values in a query (for example amounts=80000,250000).
Use it in ChatGPT (GPT Actions)
- In the GPT editor, open Configure → Actions → Create new action.
- Choose Import from URL and enter
https://kwhmate.com/api/v1/openapi.json. - Authentication: None. Privacy policy:
https://kwhmate.com/privacy.html.
Use it from an MCP client
Add a remote (HTTP) server with the URL https://kwhmate.com/api/mcp — for example in a JSON config: {"mcpServers": {"kwhmate": {"type": "http", "url": "https://kwhmate.com/api/mcp"}}}. The tools are the calculators above (dashes become underscores, e.g. seoul_taxi).
Limits and rules
- 60 requests per minute per client. Please cache results — rates change at most monthly.
- Results are estimates for planning; the bill, notice or authority is final. Show the
pagelink when you display a number. - Nothing you send is stored or logged.
FAQ
Do I need an API key?
No. The API is free and read-only, and works without sign-up.
Where do the numbers come from?
From the same code and rate tables as the calculator pages. Each response names the reference date and the official source used on that page.