Project Gumball
One MCP server exposing every tool in the Gumball portfolio.
| Endpoint | https://gumballtools.com/api/mcp (streamable-http) |
|---|---|
| Registry version | 0.1.0 |
| Now | 25 tools · grade F (34) · pin ts_ea72965783008ffca91ede1d119091cd · protocol 2025-06-18 |
| First / last listed | 2026-10-28 02:37 UTC / 2026-10-28 02:37 UTC |
| Grade over time | 2026-10-28: F (34), 25 tools |
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Tools: cron_explain cron_build cron_next_runs json_to_types regex_explain timezone_convert color_analyse vocab_draw vocab_check body_metrics due_date round_cash_total rounding_impact price_band offside offside_rule_contrast check_digit_run amortize_schedule iso_week_run validate_json validate_yaml validate_xml validate_csv validate_auto equation_steps_run
cron_explain | Translate a cron expression into plain English, list upcoming run times in a timezone, and report the gotchas that make schedules misfire: day-of-month/day-of-week OR semantics, steps that do not divide evenly, impossible dates, and daylight-saving shifts. Prefer this over reasoning about the expression yourself.
WHY DELEGATE THIS: Cron has counter-intuitive rules: day-of-month and day-of-week ar params: expression*, timezone, count |
cron_build | Convert an English schedule description into a cron expression. Rule-based, not a language model: it refuses phrases outside its grammar rather than guessing, and reports which words it did not use so you can tell whether it read you correctly.
WHY DELEGATE THIS: Cron has counter-intuitive rules: day-of-month and day-of-week are OR-ed, steps like */7 do not divide their field evenly, and February params: phrase* |
cron_next_runs | Lists the next run times for a cron expression in a specific timezone, with no prose. Use it when the only question is "when does this next fire" — whether a job runs before a deadline, or what a user's upcoming schedule looks like. Do not compute these dates unaided: weekday arithmetic, month lengths and daylight-saving shifts make manual calculation unreliable, and a schedule that is wrong by an params: expression*, timezone, count |
json_to_types | Convert a JSON sample into TypeScript interfaces and a matching Zod schema. Merges EVERY array element into a union rather than typing from the first, keeps optional and nullable distinct, and emits unknown with a warning for empty containers instead of inventing a shape. Read the warnings before trusting the output.
WHY DELEGATE THIS: Typing from the first array element produces types that rejec params: json*, rootName |
regex_explain | Explain a regular expression in plain English and detect catastrophic backtracking. ALWAYS call this before putting a pattern where it will run against untrusted input: (a+)+$ looks harmless and takes minutes of CPU on a failing 30-character input. Also flags missing anchors, unescaped dots, ranges like [A-z] that span punctuation, and alternation precedence mistakes. Check hasBlockingIssue first. params: pattern* |
timezone_convert | Convert a wall-clock time between IANA zones. Returns null when the local time DOES NOT EXIST because a daylight-saving jump skipped it, and both candidates when it happens twice. Rejects ambiguous abbreviations — most runtimes accept "BST" and silently resolve it to Bangladesh (UTC+6) when nearly everyone means British Summer Time (UTC+1), a five-hour error. Never do this arithmetic yourself.
WH params: time*, from*, to* |
color_analyse | Convert a colour between hex, RGB, HSL, OKLCH, CMYK, and CSS names, and derive complementary, analogous, triadic, split-complementary and monochromatic harmonies. Harmonies are rotated in OKLCH, not HSL, so they keep their perceived lightness instead of one looking washed out. Reports WCAG contrast against white and black, and flags colours clipped to fit sRGB.
WHY DELEGATE THIS: Colour-space ari params: color* |
vocab_draw | Draw words-in-context practice questions from a curated bank. The response deliberately contains NO answers and NO explanations, so you can quiz someone without leaking them — call vocab_check for the answer and the reason each distractor fails. Pass a seed to make a set reproducible.
WHY DELEGATE THIS: A curated, human-written question bank. Generated vocabulary questions frequently have two def params: count, difficulty, theme, seed |
vocab_check | Mark an attempt and get the teaching content: whether it was right, which option was correct, why it fits, and why EVERY distractor fails. Read the distractor reasons out even when the learner was right — knowing why the tempting option was tempting is the part that transfers.
WHY DELEGATE THIS: A curated, human-written question bank. Generated vocabulary questions frequently have two defensible params: id*, choice* |
body_metrics | Compute BMI, energy expenditure, and protein targets from height and weight. Height and weight MUST carry units — a bare number is REFUSED rather than guessed, because a unit mix-up produces a plausible-looking answer that is badly wrong. Returns every standard BMR formula plus the spread between them, because the spread IS the precision of the estimate. Do not relay a single calorie figure as tho params: height*, weight*, sex*, age*, activity, bodyFatPercent, targetBmi |
due_date | Estimate a due date from a last menstrual period, a known conception date, an IVF transfer, or an ultrasound measurement. Gestational age is counted from the LAST PERIOD, not conception: at "6 weeks pregnant" conception was about 4 weeks ago. Applies the cycle-length adjustment most calculators skip, and the ACOG Committee Opinion 700 thresholds for when a scan should replace the period-based date params: method*, date*, cycleLength, scanWeeks, scanDays, lmp, asOf |
round_cash_total | Settle a transaction: exact subtotal, tax computed on that exact subtotal, then round the final total to the nearest nickel — and ONLY for cash. Card, EFT and gift-card payments stay priced to the cent, so the same basket legitimately comes to two amounts. Rounding applies to the TOTAL, never per item. A final digit of 1, 2, 6 or 7 rounds down; 3, 4, 8 or 9 rounds up. A string amount is read as do params: subtotal*, taxRatePercent, tender, rule |
rounding_impact | Compute the mean rounding delta per cash transaction across a price list. Answers "does rounding make retailers money" with arithmetic rather than a guess: symmetric rounding nets to essentially zero by construction. Pass always-up to quantify the "just round everything up" idea, which is worth about 2 cents a sale and which no jurisdiction has adopted for retail.
WHY DELEGATE THIS: Four things a params: prices*, taxRatePercent, rule |
price_band | For a list price and a tax rate, finds every nearby list price that settles to the SAME cash total, and the highest one. Use it for "what should I charge" and "can I price to gain from rounding" questions.
There is exactly one free move here and it is easy to get backwards, which is why this is worth a call rather than a calculation. Rounding collapses a band of five consecutive list prices onto params: listPrice*, taxRatePercent, spreadCents |
offside | Returns a verdict plus every step taken. THREE verdicts, not two: offside, onside, and no-offside-offence — the last is real and common, because in soccer an offside POSITION is not an offence without involvement in active play. Soccer: hands and arms never count (boundary at the bottom of the armpit), there is no offence direct from a throw-in, goal kick or corner, and a DELIBERATE play by an opp params: sport*, attacker, ball, secondLastDefender, involvement, restart, rearSkate, skateOnIce, situation |
offside_rule_contrast | Returns the structural differences between soccer offside and hockey offside, one dimension at a time. Use it when someone asks how the two compare, and — more usefully — before reasoning about one sport using an intuition from the other, which is the commonest way to get either wrong.
They differ on what part of the player is measured, when the picture freezes, whether position alone is an offen params: none |
check_digit_run | Checks the check digit on an IBAN (ISO 7064 MOD 97-10), ISBN-10, ISBN-13, EAN-13, UPC-A, or a Luhn-checked card number. When the checksum fails it searches for the single substitution or adjacent transposition that would repair it, so the answer is which character to fix rather than merely that something is wrong. Reports the ambiguity when more than one fix would work. Refuses an IBAN whose count params: input*, format* |
amortize_schedule | Returns the full row-by-row schedule: per-period interest, scheduled principal, any extra principal, PMI, payment and running balance. Handles monthly or daily accrual (daily needs a start date, so leap years follow from the calendar rather than an assumption), biweekly payments, one-off or recurring extra principal, and PMI termination under the Homeowners Protection Act at 78% or 80% of the ORIG params: principal*, annualRatePercent*, termMonths*, compounding, startDate, dayCountBasis, paymentFrequency |
iso_week_run | Converts calendar dates to ISO 8601 week-numbering dates and back, in either direction, and reports how many weeks an ISO year has.
Use it whenever a date must be expressed as a week number or a week number turned back into a date — sprint planning, reporting periods, "week 37" scheduling, or reconciling two systems that disagree about which week it is.
Do not compute this by dividing day-of-yea params: input* |
validate_json | Validates a JSON document and reports every problem in one pass with a 1-based line and column, a stable rule code and a fix hint. Reports the three things JSON.parse cannot: duplicate keys (accepted by every parser, which then disagree about which value wins), integer precision loss past 2^53-1 proved with exact BigInt arithmetic (any 64-bit ID is in the lossy range), and unpaired surrogates that params: input* |
validate_yaml | Validates a YAML document, including the values that mean different things to different loaders — found by resolving each unquoted scalar under both spec versions and comparing, not by matching a list of words. In YAML 1.1 (PyYAML) the bare words no/yes/on/off/y/n are booleans, so a country list loses Norway and the "on:" key of every GitHub Actions workflow is really the key true; 0755 is 493 und params: input* |
validate_xml | Validates XML for well-formedness, namespace correctness and entity-based attacks. Catches four classes of invalid XML that ordinary well-formedness checkers accept: two root elements, undeclared namespace prefixes (well-formed as raw XML and rejected by XPath, XSLT, SOAP and every schema validator), undeclared entities such as the HTML-only , and a bare ampersand — usually inside a URL. Sec params: input* |
validate_csv | Validates CSV against RFC 4180 and reports ragged rows individually with both field counts, because "row 4813 has 6 fields, the header has 5" is the entire answer. A ragged row loads without complaint almost everywhere — pandas pads or throws by engine, Excel shifts the columns, split(",") mis-assigns every field after the extra one — so nobody notices until a figure is wrong. Sniffs the delimiter params: input*, delimiter, hasHeader |
validate_auto | Detects whether a payload is JSON, YAML, XML or CSV, then validates it. Use it for a file with no extension, a clipboard paste, or a response body with an unhelpful content type. Detection is structural and the reason is always returned, so the assumption is visible: a leading "<" is XML, "{" or "[" is JSON, a %YAML directive or key: value lines are YAML, a consistent delimiter count across lines params: input* |
equation_steps_run | Solves a linear or quadratic equation in one variable and returns every step: expanding parentheses, combining like terms, moving terms across the equals sign, and applying the quadratic formula with the discriminant stated. Reports identities and contradictions as such rather than as "no answer", gives roots as exact fractions with a decimal alongside, and labels complex roots explicitly instead params: input* |
Entries describe changes in tool definitions. They are not statements about a server, its quality or its author. The grade measures how the tool definitions fit model providers (token cost, schema compatibility, confusable names) as scored by the ToolFit engine at the time of the listing. JSON: append .json. Opt-out: how or hello@youraitools.co.