Each tool has a dedicated engine, declared fields and an example. Decimal monetary engines round half up to two fractional digits unless stated otherwise. Unit converters use dimension-specific factors; affine temperature conversion and differences are separate. Scientific constants and measured factors are approximate at IEEE 754 precision.
Text counts use documented segmentation. Date-only tools operate at UTC midnight and exclude the end date unless stated otherwise. Timestamp tools require an explicit offset. Regional tax tools state their year, currency and supported situation. Some report bracket tax before credits; these are not final tax bills. The UK salary tool combines income tax with an annual NI approximation and is not an exact PAYE payslip quote. Manual fee, allowance, visa and currency planners use the amounts or policies you enter.
Executable fixtures check known outputs and selected edge cases. Browser, accessibility and integration checks are reported separately in the delivery validation report. Passing local tests does not establish that GitLab authentication or a Cloudflare production deployment was tested. Correctness reports are maintained in source docs; please include tool URL, inputs and expected result in a correction report.