Every declaration carries a complete TSDoc contract

Every function-like and every type member needs a TSDoc block, with @param per parameter and @returns when something is returned.

Why it is a rule

Undocumented code forces the next reader to infer the contract from the implementation, which is how a refactor silently changes behavior. This applies to tools as much as to people: anything editing the code later works from what the declaration says about itself.

What is expected

• A /** */ block above the declaration, exported or not.
• @param for each parameter, @returns when a value is returned.
• // is for code; a // line above a declaration is documentation in the wrong form.
• Runs of // comments stay short. Longer explanation belongs in the enclosing TSDoc block.

Options

The default requires documentation on everything, module-local or not. A codebase adopting the rule late can start lower and tighten over time:

• requireOn: "exported" checks only the surface other files consume.
• requireParams: false and requireReturns: false waive the tag checks and keep only the requirement that a TSDoc block exists.
• maxInlineCommentLines moves the cap on // runs (default 2).

What is not checked

Whether the prose is any good. That remains a human question.