Explain unfamiliar code: how to do it with AI
Last checked 2026-10-15
BeginnerBot with human review 💻 Coding
Walk through what a function or file does, line by line.
1. Bot automation level
Bot with human review The bot does the work, but facts, numbers or code should be checked.
2. Before you hand it to the bot
- Gather inputs: the text, file or details the bot needs.
- Access: make sure you can use the chosen bot/plan (see limits below).
- Context: tell the bot audience, purpose, constraints and examples of good output.
- Privacy check: remove personal, confidential or regulated data unless your plan/workspace is approved for it.
- Success criteria: write down what 'done' looks like (length, format, tests passing, fields filled).
3. Copy-paste prompts
Main prompt
Explain what this function does: purpose, inputs/outputs, side effects, edge cases and possible bugs. Cite line numbers. <paste code>
Beginner-friendly
Explain what this function does: purpose, inputs/outputs, side effects, edge cases and possible bugs. Cite line numbers. <paste code> I'm new to this: explain each step in plain words and ask me for anything you need before starting.
Check-your-work
Explain what this function does: purpose, inputs/outputs, side effects, edge cases and possible bugs. Cite line numbers. <paste code> When you finish, list any assumptions you made, anything you're unsure about, and what I should double-check before using the result.
Free tiers that can handle this (verified): ChatGPT (incl. Work & Codex), GitHub Copilot, Mistral Le Chat. Others: check plan.
4. Step-by-step
- Copy the function plus its imports and any types it uses; one function at a time works best.
- Ask for: purpose, inputs/outputs, side effects, edge cases, and anything that looks like a bug.
- For a whole repo, open it in an IDE agent (Cursor Agent, GitHub Copilot agent mode, Claude Code) so it can search related files.
- Ask it to point to exact line numbers for each claim.
- Confirm 1–2 claims by running the code or a quick test.
5. Which bots and plans can do it
| Tool | What's different here | Plan limits | Source |
|---|---|---|---|
| Claude (incl. Claude Code) | Claude Code can read the whole repo from the CLI or IDE extensions. | Claude Code and Research need Pro or higher; computer use is Pro/Max only (research preview). | code.claude.com/docs/en/desktop |
| ChatGPT (incl. Work & Codex) | Codex works with local repos in the ChatGPT desktop app. | Free tier has limited deep research, Codex and Work; scheduled tasks need Go or higher (per chatgpt.com/pricing). | help.openai.com/en/articles/20001275-chatgpt-work-and-codex |
| Cursor | Cursor's Agent searches your codebase in the editor. | Pricing page unverified; cloud agents require a connected source-control repo. | cursor.com/docs/agent/overview |
| GitHub Copilot | Copilot Chat works in VS Code, JetBrains and Visual Studio. | Free: 2,000 completions + 50 chats; cloud agent listed on paid plans. | docs.github.com/en/copilot/concepts/agents/cloud-agent/about-cloud-agent |
| Mistral Le Chat | — | Free tier has limited messages, searches and coding sessions; Pro raises limits. | mistral.ai/pricing |
| DeepSeek | — | Chat app limits not documented officially; API is pay-per-token. | api-docs.deepseek.com/quick_start/pricing |
Free or paid?
- Claude (incl. Claude Code): Free plan: yes. chat, web search, files & code execution, Artifacts, connectors. Claude Code and Research need Pro. Paid: the lowest price we could verify on the official pricing page is $20/month (other plans may exist). For this task, check the plan.
- ChatGPT (incl. Work & Codex): Free plan: yes. unlimited text chats; limited uploads, images, voice, deep research and Codex. Paid: price not verified, so check the official site. Its free tier can handle this task.
- Cursor: Free: not verified, so check the official site. Paid: price not verified, so check the official site. For this task, check the plan.
- GitHub Copilot: Free plan: yes. 2,000 completions and 50 chat requests a month; agent mode and CLI. Paid: the lowest price we could verify on the official pricing page is $10/month (other plans may exist). Its free tier can handle this task.
- Mistral Le Chat: Free plan: yes. limited messages, searches, coding sessions and basic images. Paid: the lowest price we could verify on the official pricing page is $14.99/month (other plans may exist). Its free tier can handle this task.
- DeepSeek: Free: not verified, so check the official site. Paid: price not verified, so check the official site. For this task, check the plan.
6. Risks and what to double-check
- Explanations can sound right yet miss behaviour hidden in other files — check callers.
- Don't paste proprietary code into tools your employer hasn't approved.
- Run tests and review diffs; never merge unreviewed agent code.
- AI can hallucinate facts — verify anything that matters.
- Don't share secrets or other people's personal data.