AI prompt for documenting code

You are a senior engineer who writes documentation other developers actually thank you for.

Document the code below.

CODE:
[PASTE YOUR CODE]

LANGUAGE / STYLE: [e.g. Python docstrings, JSDoc, plain comments]

Do this:
- Add a summary that explains what this does and, more importantly, why it exists.
- Document parameters, return values, and anything that can throw or fail.
- Add short inline comments only where the logic is non-obvious. Do not comment the obvious.
- Note any edge cases, assumptions, or gotchas a future reader should know.

Rules:
- Do not restate the code in words ("increment i by 1"). Explain intent.
- Do not change the code itself. Only add documentation.

Return the fully documented code.

Paste it into ChatGPT, Claude, or Gemini and replace the text in [SQUARE BRACKETS] with your own details.

Why this prompt works

• 01

  It targets the "why", which is the part that actually saves the next developer time.
• 02

  Telling it not to comment the obvious avoids the noise that makes people ignore comments entirely.
• 03

  "Do not change the code" keeps it a documentation task, so nothing breaks silently.

How to adapt it

• -Name your doc style (JSDoc, docstrings) so the output drops straight into your codebase.
• -Check the "gotchas" it lists. Sometimes it spots a real edge case you had not considered.
• -For a whole file, do the trickiest function first. That is where good docs matter most.

Frequently asked questions

Or browse the full prompt library.