How I built a simple AI router to avoid vendor lock-in and costs

I've been working on a side project that needs AI for a few different tasks: answering user questions, generating image captions, and summarizing chat threads. At first, I just picked one provider (OpenAI) and called it a day. But after a month, two things became painfully clear: first, not every model is great at every task, and second, the bill was climbing fast because I was using GPT-4 for everything. So I did what any reasonable developer would do: I started swapping API keys by hand. I'd comment out one import and uncomment another, deploy, test, get frustrated, rinse and repeat.