OpenAI API
The API for accessing OpenAI's GPT models programmatically.
What is OpenAI API?
The OpenAI API lets you send prompts to GPT-4o, GPT-4 Turbo, GPT-3.5, and image/audio models, and get responses programmatically. It is the most-used LLM API in the world and the default for Indian Gen AI products.
Key features in 2026: **function calling** (let the model call your tools), **structured outputs** (force valid JSON), **vision** (send images), **assistants API** (persistent threads + tools), **prompt caching** (50% discount on repeated prefixes).
Pricing is per token. GPT-4o costs roughly $5 per million input tokens and $20 per million output tokens — meaning real production volume is expensive but reasonable at startup scale.
OpenAI API is the default Gen AI API. Every Indian Gen AI engineer is expected to know it deeply.
A Pune marketing agency uses the OpenAI Assistants API to manage long-running campaign drafting conversations across multiple brands. The thread persistence eliminated the need for custom state plumbing.
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