Rules for building something worth checking.

Arithmetic and assumptions are different things

Deterministic arithmetic should be inspectable. Real-world assumptions—fees, rates, waste percentages, product coverage, charging efficiency, overtime thresholds and similar inputs—can vary. When an assumption varies materially, the preferred design is to make it editable rather than silently hardcode it.

One page should answer one real decision

A calculator should solve a narrow problem and return outputs that help a user act. Page count is not a quality target. New pages are not created merely to swap keywords around the same formula.

Sources should be primary when a source is needed

When a calculator depends on an external rule, manufacturer specification, government guidance or protocol, tannerd.net prefers the primary publisher and records that source in the source registry. Pure arithmetic does not need a fake citation.

Externally variable numbers should be editable

Examples include marketplace fees, tax rates, dimensional-weight divisors, electricity rates, material coverage and labor premiums. A default may be offered for convenience, but it should not be presented as universal when it is not.

High-stakes boundaries

Planning calculators are not payroll records, tax returns, legal opinions, engineering approvals, medical advice or guarantees of marketplace profit. Where a result could be mistaken for one of those things, the page should say what the tool does and does not establish.

AI-assisted development

Software and content may be developed with AI assistance. The quality standard is not who typed the code; it is whether formulas, examples, links and live outputs can be inspected and tested. Public validation cases and release notes exist so the result can be checked independently.

Testing and release gates

Calculator engine tests, Worker/API integration tests and agent-protocol tests are run before packaged releases. V5.3 additionally publishes a subset of regression cases for anyone to run against production.

Corrections

Corrections should change the formula, explanation or source transparently, receive a new release entry when meaningful, and preserve a public record in the changelog.