Vibe coding prompts that work. Say what done looks like, start small, and make the agent prove it runs.
Say what done looks like
Weak: “make a budget app”. Strong: “a web page where I add expenses with an amount and a category, see the total per category, and the list survives a reload”. The agent stops when that is true.
Start small, then grow it
Ask for the smallest version that works, run it, then add one thing per follow-up: “now add a chart of the totals”. Small steps are easier to check and to undo.
Ask for a plan before a big change
For anything bigger than one screen: “plan how you would add sign-in; do not write code yet”. Read the plan, answer its questions, then say “build it”.
Make it prove it works
“Run it and fix every error before you stop.” “Add a test for the totals and make it pass.” MegaBrain runs your commands and tests itself, so it checks its own work instead of guessing.
Say what not to touch
“Change only the header; leave the rest of the page as it is.” A limit keeps a small fix from turning into a rewrite.
When it goes wrong
Paste the error as it is, or say what you saw: “the button does nothing”. Or: “that broke the list; undo your last change and try another way”.
Questions
What is a good vibe coding prompt?+
One that says what the result should do and how you will know it works, in plain words: “a page with a search box that filters my list of books by title as I type”. Leave the how to the agent unless you care.
Should I tell the AI which language or framework to use?+
Only if you care, or if your project already has one. In an existing project the agent reads the code first and follows what is there.
How long should a prompt be?+
As long as it takes to say what done looks like: one to three sentences for a small feature. For a big change, ask for a plan first and answer its questions.
What do I do when the code does not work?+
Paste the error, or describe what you saw, and ask the agent to run the app and the tests itself and fix what fails.
Where can I try these prompts for free?+
In MegaBrain. Free costs nothing and needs no card: the agent in your terminal, your editor and the Mac app, the free models, and your own API keys and local models (Ollama, LM Studio) with no limits from us.
More free AI coding tools
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Cursor Alternative with a Free Plan
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Free Vibe Coding in VS Code
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Free AI Coding Agent for JetBrains IDEs
IntelliJ IDEA, PyCharm, WebStorm, GoLand, Rider and the rest: an agent that plans, edits across files and runs your tests.
Vibe Coding with Local Models
Run the agent on a model on your own machine, served by Ollama or LM Studio. Free, with no limits from us.