AI Developer (Level 7)
Topic Guide · 2026
OpenAI API
OpenAI API guide — Chat Completions, Responses API, Assistants, function calling, structured outputs, embeddings and Realtime.
Quick Answer
The OpenAI API is the most popular way to build with GPT-5. It exposes Chat Completions, the new Responses API, structured outputs, embeddings, image and audio endpoints.
What you'll learn
- Chat Completions vs Responses API
- Function calling and tools
- Structured outputs (JSON mode)
- Embeddings and vector search
- Vision and image generation
- Realtime API for voice
- Cost, rate limits, streaming
Recommended tools
OpenAI PlatformOpenAI Python SDKOpenAI Node SDK
Frequently asked questions
How much does the OpenAI API cost?+
GPT-5 mini: $0.25/M input, $2/M output. GPT-5: ~$2.50/M input, $10/M output. Most SME workflows cost under $50/month.
Chat Completions or Responses API?+
New projects — use Responses API. It has native tools, state, and streaming. Existing production — Chat Completions is still fully supported.
Want OpenAI API training for your team?
Nirmal Rabari delivers this topic as a live corporate workshop across India, UAE, UK and US.