Sindri

Periodic table element lookup by symbol or atomic number, returning name, atomic mass, and category. Covers the most commonly referenced elements.

Base64 encoder API. Encodes UTF-8 text to base64 instantly and correctly — skip burning agent tokens hand-computing base64, which LLMs frequently get wrong on padding and edge cases.

Checksummed-financial-identifier generator API. Generates a structurally valid iban, bic, creditCardNumber, bitcoinAddress, litecoinAddress, ethereumAddress, or routingNumber, each computed with its real checksum algorithm (mod-97, Luhn, EIP-55, etc.). Accepts optional locale (default en_US).

Network-format generator API. Generates a valid ipv4/ipv6 address (optionally within a CIDR block or named network range) or a well-formed JWT string (via one of: ipv4, ipv6, jwt). Accepts optional locale (default en_US). jwt header/payload objects are capped to 2000 serialized characters.

Secure password generator API. Generates a cryptographically random password — true randomness an LLM cannot produce on its own. Accepts optional length (8-128), per-character-class toggles (uppercase/lowercase/numbers/symbols) with guaranteed inclusion, and a pronounceable easy-to-say mode.

True-random-string generator API. Generates a bounded random string via one of: alpha, alphanumeric, binary, octal, hexadecimal, numeric, sample, uuid, ulid, nanoid, symbol. Accepts optional locale (default en_US). length/count-style args are capped to 0-1000.

Live weather API. Returns real-time weather conditions, temperature, feels-like temperature, humidity, wind speed, precipitation, and UV index for any city worldwide — live external data an LLM cannot know on its own. Supports metric/imperial units, 74 languages, and optional 3-day forecast and sun/moon astronomy data.

House hacking calculator. Nets rental income from other units/rooms against your mortgage payment and expenses, then adds back the equity you build via principal paydown and the market rent you avoid paying elsewhere, to compute the true monthly net-worth impact of living in and renting out part of a property.

Upwork freelancer fee calculator. Applies a documented tiered marginal service-fee schedule (20%/10%/5% at $500/$10,000 cumulative per-client lifetime billing thresholds) to compute take-home pay on an invoice, correctly splitting fees across a tier boundary like a tax bracket. Platform fee policies can change; verify current rates before relying on this for financial decisions.

15-year vs 30-year mortgage comparison calculator. Computes monthly payment and total interest for both loan terms on the same purchase price and down payment, and reports the payment and lifetime-interest tradeoff between them.

URL validation API. Checks whether a string is a syntactically valid URL, catching malformed schemes, hosts, and encoding edge cases a naive check misses. Returns true or false.

Email validation API. Checks whether a string is a syntactically valid email address using the same production-grade validation library trusted across the Node.js ecosystem, catching edge cases a quick regex misses. Returns true or false.

Barista FIRE calculator. Simulates net worth growth through a full-time-saving phase and then a reduced-target phase funded partly by part-time/side income after quitting full-time work, until full financial independence is reached.

Scientific unit conversion for pressure, energy, and molarity using exact conversion factors.

Line-based diff between two strings using the Myers diff algorithm (via the diff/jsdiff library), returning a list of equal/add/remove operations.

Base64 decoder API. Decodes a base64 string back to UTF-8 text instantly and correctly, avoiding the padding and charset errors LLMs make when decoding base64 by hand.

Arbitrary-precision integer arithmetic (add, subtract, multiply, power) beyond IEEE-754 float precision, using native BigInt. Operands are passed as digit strings so precision is never lost in transit. For power, the combined magnitude (base digit count x exponent) is capped at 50000 to bound response size, in addition to the per-operand digit cap and exponent cap.

Cap rate calculator for real estate investing. Runs a full multi-year deal analysis (per-category rent/expense growth, a sale scenario, IRR) and headlines the capitalization rate: first-year NOI divided by purchase price.

Coast FIRE calculator. Computes the lump sum needed today, invested with zero further contributions, to grow into your full retirement number by your target retirement age, plus (given an ongoing monthly contribution) a year-by-year projection of when your actual trajectory crosses that lump sum.

Converts a color between hex, rgb, and hsl representations using exact arithmetic.

Computes the next N run times for a standard 5-field cron expression, avoiding the mental cron-schedule simulation an LLM often gets subtly wrong.

Emergency fund calculator. Multiplies monthly essential expenses by a chosen runway length (in months) to compute a target emergency savings amount.

Safe arithmetic expression evaluator. Parses and evaluates expressions with +, -, *, /, ^, and parentheses using a bounded-recursion parser (no eval/Function), avoiding the arithmetic slips an LLM makes on long expressions.

Fat FIRE calculator. Same year-by-year compound-growth simulation as the standard FIRE calculator, framed for a higher, more lifestyle-preserving retirement spending target.

FIRE (Financial Independence, Retire Early) calculator. Projects year-by-year net worth growth to determine how many years until your portfolio can sustainably fund retirement spending at a given safe withdrawal rate — precise compound-growth simulation an LLM cannot reliably run mentally. incomeGrowthRate is deflated by inflationRate internally. Past retirementAge the simulation draws down retirementAnnualSpending with no further income.

True-random-geo-coordinate generator API. Generates a bounded random latitude, longitude, or a coordinate near a given origin (via one of: latitude, longitude, nearbyGPSCoordinate). Accepts optional locale (default en_US). Numeric args are capped to +/-1e15; precision is capped to 0-20; origin must be a [latitude, longitude] pair.

True-random-number generator API. Generates a bounded random number via one of: int, float, binary, octal, hex, bigInt (returned as a string), romanNumeral. Accepts optional locale (default en_US). Numeric args (min, max, multipleOf) are capped to +/-1e15; fractionDigits is capped to 0-20.

Slug generator API. Converts any text into a clean, URL-safe slug (lowercase, hyphen-separated, unicode-aware), handling punctuation and accented-character edge cases a naive regex misses.

Live currency exchange rate API. Returns the current exchange rate between any two ISO 4217 currency codes (e.g. USD to EUR) — live external data an LLM cannot know on its own.

UUID generator API. Generates a random RFC 4122 version 4 UUID using a cryptographically secure source — not the pseudo-random, collision-prone IDs an LLM would invent. No input required.