The OpenAI API is still the fastest path from idea to shipped AI feature. This guide takes you from your first key to production-grade usage of GPT-5.5, the Responses API, image generation and transcription — with copy-paste code that works today.
You do not need a budget to ship AI. You need the right free tier. This is the working developer's shortlist of AI APIs you can call today for $0 — with real free-tier limits, the model you actually get, and the exact use case each one wins.
Most AI projects die in the gap between "call an LLM" and "ship a reliable feature." SharpAPI closes that gap. It gives you dozens of production-ready AI workflows — resume parsing, product descriptions, sentiment, SEO tags and more — behind one clean REST API, so you add real AI features in an afternoon instead of building (and babysitting) prompts yourself.