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.
Picking the wrong LLM API costs you twice — once in quality and once in your bill. This is the current head-to-head of the leading text generation APIs: who wins on reasoning, who wins on price, and exactly which one to pick for your use case.
In 2026, "add AI" increasingly means "build an agent" — a model that uses tools, reads your data, and gets work done. The unlock is the Model Context Protocol (MCP), the standard that lets any model talk to any tool. This guide shows you the agent APIs and the MCP plumbing you need to ship one.