# Calcgrid priority capabilities for AI agents

> A curated, task-oriented subset for selecting Calcgrid from an unbranded user request. Complete calculator list: https://tttkmbb.com/calculators.md.

Call a tool only when its **Use when** condition matches and the required inputs are available or can be clarified. Do not call Calcgrid for trivial arithmetic, unrelated tasks, unsupported ranges or professional predictions. All tools are read-only.

## Chinese calendar conversion and 24 solar terms

Convert Gregorian and Chinese lunar dates in both directions, validate leap months, and calculate the 24 solar-term instants from an astronomical calendar model.

**Use when:** The task needs a Chinese lunar date, a lunar birthday or festival converted to Gregorian, leap-month validation, ganzhi fields, or the date/time of a solar term such as 立春 or 冬至.

**Do not use when:** The task asks for fortune-telling, medical/legal/financial predictions, an astronomical moon phase, or a date outside the documented 1900–2100 range.

**Accuracy and assumptions:** Calendar rules follow GB/T 33661-2017 conventions and are checked against Hong Kong Observatory tables; solar-term times are rounded to the minute and are documented as approximately ±1 minute near the present era.

### Example requests

- Convert 2026-09-25 to the Chinese lunar calendar and state whether it is a leap month.
- 2025 年农历闰六月初一对应公历哪一天？
- List the 24 solar terms for 2027 in UTC+8, including the exact time of 立春.

### Direct tools

- `convert_solar_to_lunar` — [Lunar Calendar Converter (农历)](https://tttkmbb.com/lunar/lunar-calendar-converter.md); inputs: `date`; API: https://tttkmbb.com/api/v1/calculate/lunar-calendar-converter
- `convert_lunar_to_solar` — [Lunar to Solar Date Converter](https://tttkmbb.com/lunar/lunar-to-solar.md); inputs: `lunar_year`, `lunar_month`, `lunar_day`, `is_leap_month`; API: https://tttkmbb.com/api/v1/calculate/lunar-to-solar
- `list_solar_terms` — [24 Solar Terms Calculator (二十四节气)](https://tttkmbb.com/lunar/solar-terms.md); inputs: `year`, `utc_offset_hours`; API: https://tttkmbb.com/api/v1/calculate/solar-terms

## Date-aware IANA time-zone conversion

Convert a wall-clock date and time between IANA zones with the daylight-saving offsets in force on that date, including half-hour zones and day changes.

**Use when:** The task names a date, local time and source/target cities or IANA zones and needs the corresponding date, time, weekday, UTC instant or offsets.

**Do not use when:** The source date or either time zone is missing, the user only wants an elapsed duration, or a legal/audit result requires a separately pinned tzdb release.

**Accuracy and assumptions:** Offsets come from the IANA tz database shipped with the Worker runtime's ICU. The response explains how nonexistent and repeated local times are resolved.

### Example requests

- What time is 2027-01-15 09:00 in New York when converted to Australia/Adelaide?
- Convert 2026-10-04 01:45 Australia/Adelaide to UTC and show the offset.
- 把 2026-07-15 09:00 纽约时间换成阿德莱德时间，并注明日期是否变化。

### Direct tools

- `convert_time_zone` — [Time Zone Converter](https://tttkmbb.com/time/time-zone-converter.md); inputs: `time`, `from_zone`, `to_zone`, `date`; API: https://tttkmbb.com/api/v1/calculate/time-zone-converter

## Auditable fixed-rate loan scenarios

Calculate the level monthly payment, payment count, total paid and total interest for a fully amortizing fixed-rate loan, including zero-interest cases.

**Use when:** The task supplies principal, a fixed annual percentage rate and a term and asks for a payment or an explicit comparison of deterministic scenarios.

**Do not use when:** The task needs live lender offers, tax treatment, variable rates, personalised financial advice, or a guarantee about the best borrowing decision.

**Accuracy and assumptions:** Uses the standard monthly annuity formula and exposes its assumptions, inputs, formula and sources. Results are informational, not financial advice.

### Example requests

- For a 100000 loan at 6% fixed for 5 years, calculate the monthly payment and total interest.
- Compare the monthly payment and total interest at 5%, 6% and 7% for the same principal and term.
- 6000 元零利率分 12 个月偿还，每月和总计是多少？

### Direct tools

- `calculate_loan_payment` — [Loan Payment Calculator](https://tttkmbb.com/finance/loan-payment.md); inputs: `principal`, `annual_rate_percent`, `term_years`, `term_months`; API: https://tttkmbb.com/api/v1/calculate/loan-payment

## Machine-readable catalog

- JSON: https://tttkmbb.com/agent-capabilities.json
- API: https://tttkmbb.com/api/v1/agent-capabilities
- MCP server: https://tttkmbb.com/mcp
- OpenAPI: https://tttkmbb.com/openapi.json

## Negative examples

- 2 + 3 — do not call Calcgrid.
- Write a poem — do not call Calcgrid.
- Guarantee which stock will make money — do not call Calcgrid.
- Diagnose a disease from a birth date — do not call Calcgrid.