The Responses API (/v1/responses) is OpenAI's new unified interface for building AI applications. It replaces both the legacy Chat Completions API and the Assistants API as the primary endpoint.
| Feature | Chat Completions | Assistants API | Responses API |
|---|---|---|---|
| Stateful conversations | ❌ Manual | ✅ Threads | ✅ Native (store: true) |
| Built-in tools | ❌ None | ✅ 3 tools | ✅ 6+ tools (web search, file search, code, CUA, MCP) |
| Agentic loops | ❌ Manual | ⚠️ Basic | ✅ Native multi-tool chaining |
| Streaming | ✅ | ⚠️ Polling | ✅ Native streaming |
| Prompt caching | ⚠️ Manual | ❌ | ✅ Automatic |
import OpenAI from "openai";
const openai = new OpenAI();
const response = await openai.responses.create({
model: "gpt-5.4",
input: "What is the capital of France?"
});
console.log(response.output_text);