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Reckon — connector documentation

  • MCP endpoint: https://reckon.connectorbay.com/mcp
  • REST API: POST https://reckon.connectorbay.com/v1/tools/{tool_name}, described by the OpenAPI 3.1 spec at https://reckon.connectorbay.com/openapi.json
  • Transport: Streamable HTTP, stateless, MCP specification 2025-06-18 or later
  • Authentication: none required. An optional Authorization: Bearer <key> raises rate limits.
  • Health: https://reckon.connectorbay.com/health · Tool schemas: https://reckon.connectorbay.com/tools.json
  • Publisher: Unify Dynamics LLC · connectorbay.com/reckon · agent@connectorbay.com

What Reckon is for

The arithmetic that comes up every day and that assistants get subtly wrong: the pre-tax price hiding inside a tax-inclusive total, margin versus markup, whether a 750 g pack at 4.99 beats a kilo at 6.49, what a 30-year mortgage really costs with an extra 200 a month, how many grams two cups of flour are (not the same as two cups of sugar), and which EU shoe size a US 9 is. Reckon computes each from the published definition and returns the working so the answer can be checked.

What it does

Units in 14 categories with 200+ names and aliases, including fuel economy (mpg ↔ L/100 km), data (KB vs KiB) and South Asian land units. Currency at the ECB's reference rate for today or any date since 1999. Percentages in nine forms. Tips and bill splitting. Loan amortisation with extra payments and a year-by-year schedule. Compound growth with contributions, effective rate, doubling time, inflation adjustment and the contribution needed to hit a goal. BMI, healthy-weight range, BMR and daily calories (Mifflin–St Jeor). Cooking conversions by ingredient density for 60 ingredients. Shoe, clothing and ring sizes across systems. Fuel cost of a trip. Unit-price comparison. Numbers as words in English and Indian style, Roman numerals, ordinals and bases.

What it is not

Reckon is not financial, medical or legal advice: loan maths ignores fees and taxes; BMI and calorie figures are population formulas; ECB rates are mid-market, not what a bank charges. Size charts are the common standards and brands deviate.

Tools

Units & money

convert_units — Convert between units — length, mass, volume, area (incl. acre, hectare, bigha, guntha), speed, time, energy, power, pressure, data (KB vs KiB), angle, frequency, fuel economy (mpg ↔ L/100km ↔ km/L) and temperature (C/F/K). 200+ units. Use for "5 miles in km", "80 F in C", "3 acres in square metres", "30 mpg in litres per 100 km", "2 TB in GiB". Args: value, from_unit, to_unit.

units — The unit categories and unit names Reckon understands (for convert_units).

currency — Convert money between 30 major currencies at the European Central Bank's daily reference rate — today's or any past date's — with the rate and its date. Use for "$250 in rupees", "100 euros in yen last Friday", "what was the pound worth in dollars on 1 Jan 2020". Args: amount, from_currency, to_currency, on_date.

Percentages & bills

percent — Percentage arithmetic done right: X% of Y; percent change from A to B; A is what % of B; the original before a percentage was added (pre-tax, pre-discount); add or subtract a percentage; markup vs margin; split a tax-inclusive price into net and tax. Use for "18% GST on 4,500", "from 80 to 92 is what % increase", "118 includes 18% tax — what's the net", "price for 30% margin on a cost of 70". Args: operation, x, y.

tip_split — Tip and split: the tip amount, total with tip (and tax if you add it), each person's share, and rounded-up shares if you want tidy numbers. Use for "15% tip on 84.50 split 3 ways", "we're 6 people, bill 230 plus 8% tax and 18% tip". Args: bill, tip_pct, people, tax_pct, round_up.

Loans & savings

loan — Amortising loan or mortgage maths: the payment, total interest and total paid, how an extra payment shortens the term and saves interest, and a year-by-year breakdown of interest, principal and balance. Use for "mortgage on 400k at 6.5% over 30 years", "car loan 25k at 9% for 5 years", "what if I pay 200 extra a month". Args: principal, annual_rate_pct, years, extra_monthly, payments_per_year.

compound_interest — Compound growth: future value of a lump sum plus regular contributions, interest earned, effective annual rate, doubling time (exact and rule of 72), inflation-adjusted value, and — given a goal — the contribution needed to reach it. Use for "10k at 7% for 20 years with 200 a month", "how much to save monthly to reach 1 crore in 15 years at 12%". Args: principal, annual_rate_pct, years, contribution, contributions_per_year, compounds_per_year, inflation_pct, goal.

Body, kitchen, wardrobe

body_metrics — BMI with the WHO category and healthy-weight range for the height, and — with age and sex — basal metabolic rate (Mifflin–St Jeor), daily calories by activity level and the intake for ±0.5 kg/week. General wellness numbers, not medical advice. Use for "BMI for 178 cm and 72 kg", "how many calories does a 35-year-old woman, 165 cm, 60 kg, moderately active need". Args: height, weight, age, sex, activity.

cooking — Cooking conversions by ingredient — cups, tablespoons, teaspoons, millilitres, sticks ↔ grams, ounces, pounds — using each ingredient's density (flour ≠ sugar ≠ butter), for 60 common ingredients including Indian staples. Use for "2 cups flour in grams", "200 g butter in sticks", "how many tablespoons is 30 g honey". Args: ingredient, amount, from_unit, to_unit.

sizes — Convert clothing, shoe and ring sizes between US, UK, EU and metric systems — men's and women's shoes (with foot length in cm), women's numeric and letter sizes, men's chest sizes, ring sizes by US/UK/circumference/diameter. Use for "US 9 men's shoe in EU", "what's a UK 12 dress in US", "ring size 54 mm in US". Args: kind, size, region, sex.

Everyday

fuel_cost — Fuel needed and cost for a trip from distance, efficiency (L/100 km, km/L or mpg) and price, optionally round trip and split between passengers. Use for "fuel cost Denver to Santa Fe at 32 mpg and $3.40 a gallon", "350 km at 6.5 L/100km with petrol at 1.65". Args: distance, efficiency, fuel_price, distance_unit, efficiency_unit, price_unit, round_trip, passengers.

unit_price — Which offer is the better value: normalises each to a price per common unit (per kg, per litre, per item) and ranks them, with the saving versus the dearest. Use for "750 g for 4.99 or 1 kg for 6.49", "12-pack for 8 vs 18-pack for 11". Args: offers.

number_format — A number every way: words (English and Indian lakh/crore), international and Indian digit grouping, scientific, Roman numerals, ordinal, binary/octal/hex, and lakh/crore/million equivalents — accepting shorthand like '2.5 lakh', '1.2M' or a Roman numeral as input. Use for "12345678 in words", "how much is 3 crore in millions", "1994 in Roman numerals". Args: number.

Conventions

  • Read-only. Every tool reads public data or computes; nothing is written anywhere and nothing about the user is stored.
  • Result envelope. ok: true with data, or ok: false with a structured error (bad_input, not_found, upstream_error). degraded lists optional sources that were unreachable.
  • Rate limits. Free tier 60 tool calls/minute and 300/day per user (keyed on the user identifier supplied by the host agent, else client IP); Pro keys raise this. Over-limit calls return HTTP 429 with Retry-After. initialize and tools/list are never counted.

Support

agent@connectorbay.com · connectorbay.com/reckon/support