the402 x402 endpoint directory

Register a standing watch over a set of URLs and pre-buy pull credits. POST {"urls":[...],"credits":10}; we keep those

Verify whether a supplied public source page currently supports one atomic factual claim. Returns supported, contradic

Base USDC lending APY. Live USDC lending yield on Base, read on-chain: Aave V3 USDC vs Morpho Gauntlet USDC Prime. Siz

Compares two semantic version strings and reports which is greater, lesser, or equal, using the standard semver compar

Decodes (does not verify) a JWT by base64url-decoding its header and payload segments. Signature validity is never che

Generates a QR code for the given text, returned as a base64-encoded PNG data URL, computed entirely locally with no e

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

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

Validates a JSON document against a JSON Schema using the industry-standard ajv validator, returning whether it is val

Tests a regular expression pattern against a string, guarded against catastrophic backtracking (ReDoS) by running the

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

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

Lookup of standard physical constants (speed of light, gravitational constant, Planck constant, elementary charge, Avo

Sunrise, sunset, solar noon, day length, and moon phase for a given latitude/longitude/date, computed via the suncalc

Descriptive statistics summary (mean, median, variance, standard deviation, and 25th/75th/90th percentiles via linear

Deterministic primality test using the Miller-Rabin algorithm with a witness set proven deterministic for all integers

Prime factorization of an integer via trial division, returning the full list of prime factors (with repetition).

Solves a system of linear equations (Ax = b) using the ml-matrix library's LU decomposition (LuDecomposition), with a

Unit conversion for length, mass, volume, and temperature using exact conversion factors (temperature uses the correct

Matrix operations: multiply, transpose, determinant, and invert, for matrices up to 20x20. Uses the ml-matrix library'

Arbitrary-precision integer arithmetic (add, subtract, multiply, power) beyond IEEE-754 float precision, using native

Safe arithmetic expression evaluator. Parses and evaluates expressions with +, -, *, /, ^, and parentheses using a bou

Tesla savings calculator. Compares annual electricity cost for a Tesla against annual gas cost for a comparable gas ve

Electric car savings calculator. Compares annual electricity cost against annual gas cost for a comparable gas vehicle

Hybrid vs gas savings calculator. Compares annual fuel cost between a hybrid and a conventional gas vehicle based on m

Gas mileage savings calculator. Compares annual fuel cost between two gas-powered vehicles based on miles driven, gas

Alcohol spending and opportunity-cost calculator. Sums home and going-out drinking costs plus associated rideshare cos

Upwork freelancer fee calculator. Applies a documented tiered marginal service-fee schedule (20%/10%/5% at $500/$10,00

HSA (Health Savings Account) growth calculator. Projects year-by-year account balance from a starting value, annual co

Keeping up with inflation calculator. Computes the pre-tax raise needed under two scenarios — keeping the same dollar

Emergency fund calculator. Multiplies monthly essential expenses by a chosen runway length (in months) to compute a ta

Savings rate calculator. Divides the gap between monthly take-home income and spending by income to produce your perso

Portfolio rebalancing calculator. Given current holdings and target allocation percentages, computes the dollar gap pe

House hacking calculator. Nets rental income from other units/rooms against your mortgage payment and expenses, then a

Rental property investment calculator. Full multi-year deal analysis for a rental property deal: mortgage, per-categor

Cash-on-cash return calculator for real estate investing. Runs a full multi-year deal analysis (per-category rent/expe

Cap rate calculator for real estate investing. Runs a full multi-year deal analysis (per-category rent/expense growth,

Compound interest calculator. Projects the ending value of an investment given a starting principal, monthly contribut

15-year vs 30-year mortgage comparison calculator. Computes monthly payment and total interest for both loan terms on

Loan payment calculator. Computes the fixed monthly payment for a standard amortizing loan and returns the full month-

Purchase impact on FIRE timeline calculator. Runs the FIRE net-worth simulation twice — with and without a one-time pu

Windfall impact on FIRE timeline calculator. Runs the FIRE net-worth simulation twice — with and without a one-time lu

Barista FIRE calculator. Simulates net worth growth through a full-time-saving phase and then a reduced-target phase f

Fat FIRE calculator. Same year-by-year compound-growth simulation as the standard FIRE calculator, framed for a higher

Coast FIRE calculator. Computes the lump sum needed today, invested with zero further contributions, to grow into your

FIRE (Financial Independence, Retire Early) calculator. Projects year-by-year net worth growth to determine how many y

Live weather API. Returns real-time weather conditions, temperature, feels-like temperature, humidity, wind speed, pre

Live cryptocurrency price API. Returns the current market price (in USD) of any cryptocurrency by ticker symbol (BTC,

Live currency exchange rate API. Returns the current exchange rate between any two ISO 4217 currency codes (e.g. USD t