I Blew €400 on Cursor — Here's What I Learned So You Don't Have To

I spent 400 Euros with Cursor in a couple of days… and these are my lessons learned. Building software with Cursor is super fast, and you should definitely use it. However, there are some downsides. AI can fail to keep your code consistent and can introduce vulnerabilities into your application.

So these are my tips:

1. Don't use "Free" or "Premium" models. Coding with them is like coding with a "junior programmer." As I like to say, a junior programmer is the most expensive programmer in a company—the result of their work is spaghetti code that somehow works, but nobody wants to touch it again, and everything needs to be refactored. The exception is the use of gpt-4o if you want to include an image in your request (for example, if you have a design that you would like to build).
2. The most expensive model is chatGPT 4.5-preview (costs 2 Euros per request via Cursor). However, at the moment of writing this blog, the performance is not worht it. Don't use it; don't waste your money.
3. Use the o1 model. It's not included in Free or Premium models; you need to allow it in Cursor account settings under "Enable usage-based pricing." If used via Cursor, it costs 40 cents per request. Is it expensive? It depends on how much you charge. If you save 15 minutes with such a request, how much did you actually earn?
4. Use your own API key for OpenAI. It is much cheaper. Moreover, there is a promo on the OpenAI platform where you get 10 million tokens daily for free if you share data with them—so you can pretty much build anything for free. (Available until April 30th, 2025, for some users.)
5. Allow a large context—requests will use more tokens, but it's worth it for better results and better consistency. In Cursor, go to Settings → Features → Chat & Composer.
6. Use default instructions (Rules for AI and Project rules in Cursor settings). Once you decide to use a library, add it to the default instructions. For example, if you decide to use HeroIcons, add it to your context. Otherwise, you might end up sometimes using lucide-icon, sometimes HeroIcons, and sometimes it creates an entire SVG icon from scratch.
7. Use a reference file to help with consistency. If you have one API endpoint ready and you're going to build another one, provide the existing file as a reference. For example, "Create a CRUD API endpoint for resources using the similar approach as in projects/routes." This helps maintain consistency.
8. Do the PR review. Sometimes it removes important parts; sometimes it introduces vulnerabilities. For now, you shouldn't use Cursor for complex projects with user data stored if you have no idea what you are doing.
9. Don't use paid or brand-new libraries. This makes sense if you think about it: AI is trained on available data, and there is much more vanilla JavaScript in public repos than use-cases for some paid libraries. Also, documentation is often not sufficient and can be unclear even to humans. However, you can build pretty much anything very fast with vanilla code.
10. Focus on providing the right context. This is pretty obvious, but it's actually crucial—if the context is incorrect, AI will try to fix the wrong issue. If you struggle to fix or build something, reconsider your context and try again.

I built my micro SaaS, in a couple of days with Cursor. Curious about results? Check out my profile for link.