jsdoc

JSDoc

Add JSDoc only where a careful reader cannot infer intent, constraints, or failure modes from names and types alone. Prefer TypeScript types for shape; use JSDoc for why, when, and what breaks.

When to Document

Document a symbol when any of these are true:

• Control flow, algorithm, or state machine is non-obvious on first look.
• Behavior depends on invariants, ordering, timing, idempotency, or concurrency.
• Side effects matter (I/O, mutation, cache, network, timers, global state).
• Failure modes, throws, empty results, or partial success are part of the contract.
• Units, ranges, formats, or domain meanings are not clear from the type.
• Public / exported API that callers will use without reading the implementation.
• Deprecation, migration, security, or compatibility constraints apply.

When Not to Document

Skip JSDoc when:

• The name + TypeScript types already explain the symbol.
• The body is a trivial getter, setter, passthrough, or one-liner map/filter.
• The comment would only restate the parameter or return type.
• The comment narrates what the next line does (// increment i).
• Generated code, tests that are self-describing fixtures, or vendored files (unless documenting a public test helper).

Default: no comment. Silence is better than noise.

TypeScript Rules

1. Types carry the shape. Do not duplicate types in JSDoc (@param {string} id) when the signature already has id: string.
2. JSDoc carries meaning. Use prose + selective tags for behavior types cannot express.
3. Prefer @param name / @returns descriptions without type braces when documenting TS.
4. Keep the first sentence a summary of behavior or purpose, not a restatement of the symbol name.
5. Document non-obvious generics with a short note on what T represents and any constraints beyond the type bound.
6. For overloads, document each distinct call pattern; put shared caveats on the implementation or the primary export.
7. Match existing project JSDoc style (tag set, punctuation, @returns vs @return) when one is already dominant.

Required Content for Documented Symbols

Every JSDoc block you add must include:

1. Summary — one sentence: what it does or why it exists (not “This function…” fluff).
2. Non-obvious details — only what a reader would miss: invariants, ordering, side effects, edge cases, units, security.

Add tags only when they earn their keep:

Tag	Use when
@param	Param semantics, units, valid ranges, or “must be…” constraints beyond the type
@returns	Meaning of the value, empty/sentinel cases, or “never returns” style contracts
@throws	Documented error conditions callers should handle
@example	Non-trivial usage that types alone do not teach (keep short; one example usually enough)
@see	Related symbol, RFC, ticket, or algorithm source
@deprecated	Replacement path and removal intent
@template	Only in JS files or when documenting a generic’s role; prefer TS type params in .ts

Do not invent tags the project never uses. Prefer standard JSDoc/TS-supported tags.

Workflow

1. Scope — files, symbols, or “public API only” as the user named. If unclear, prefer exported / complex symbols over private helpers.
2. Scan — find candidates using the “When to Document” list. Skip obvious code.
3. Audit existing JSDoc — remove or rewrite comments that restate types, lie about behavior, or narrate the obvious.
4. Write — add concise blocks; prefer editing the symbol in place over separate doc files.
5. Verify — re-read: would a new teammate understand the hard parts without opening every callee? Types still match the prose?

Quality Bar

Good JSDoc:

• Explains a constraint or failure mode you cannot see from the signature.
• Stays accurate if implementation details change under the same contract.
• Is shorter than the code it documents whenever possible.

Bad JSDoc:

• @param id - The id
• @returns {Promise<User>} when the signature already says that
• Essays that duplicate the function body
• Outdated comments that contradict the code (delete or fix; never leave lying docs)

Examples

Concrete good/bad patterns: examples.md.

Completion

When asked to document a scope, report briefly:

• What was documented and why it qualified.
• What was left undocumented (and that it was intentional).
• Any JSDoc removed as noise or corrected as wrong.