The Responses API supersedes Chat Completions as OpenAI's recommended API for all new projects. It's not just a rename — it's a fundamentally richer interface designed for the agentic era.
Key Advantages
- Stateful conversations via
previous_response_id— no need to resend message history. - Built-in tools — web search, file search, code interpreter, image generation, computer use, and MCP, all without external orchestration.
- Semantic SSE events — typed streaming events instead of raw deltas.
- 3% improvement on SWE-benchmark vs Chat Completions with the same prompt.
- 40–80% better cache utilization in internal tests.
- Lower code complexity for multi-turn and agentic workflows.
The Responses API uses input instead of messages, instructions instead of a system role, and provides an output_text convenience property. The store parameter defaults to true, enabling multi-turn with previous_response_id out of the box.