Write docstrings for code

Why this prompt works

• →Banning parameter-restating docstrings targets the default LLM failure directly: verbose, technically complete docstrings that add zero information over the function signature.
• →Asking specifically for edge cases and error conditions gets the part of a docstring that's genuinely hard to infer from a casual read — what happens at the boundaries.
• →Permission to skip self-explanatory functions keeps the output honest — blanket docstring coverage otherwise turns into noise that buries the functions that actually needed it.

Part by part

what it does (behaviour, not implementation)

The distinction that separates a useful docstring from a paraphrase of the body. Implementation changes; documented behaviour is a contract.

the edge cases and error conditions it handles or explicitly doesn't

Asks for the negative space, which is what callers actually need and what reading the signature cannot give them.

every parameter line must add information the signature doesn't already give

The rule that prevents the most common failure — restating parameter names as prose. Units, ranges and null meaning are the useful additions.

Skip any function that's already self-explanatory

Explicit permission to write nothing. Without it a model documents every getter, which adds noise and buries the docstrings that matter.

Common mistakes

• Add docstrings to this code.

  Produces a docstring per function that restates the name and lists the parameters, including trivial ones. The output looks like documentation and tells a reader nothing they could not see.

• Document this code thoroughly.

  Thorough is read as more words, so every function gets a paragraph and the important caveats are diluted. Specifying what each line must add is what constrains the volume.

• Explain what this code does.

  Asks for a description of the implementation, which becomes wrong the moment the implementation changes. A docstring should describe the contract, not the current mechanism.

Questions