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Why Responses API?

🚀 The Responses API 12 min 200 BASE XP⌨ HANDS-ON LAB

The New Standard (2025–2026)

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.

Why the Migration?

FeatureChat CompletionsAssistants APIResponses 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

Basic Usage

import OpenAI from "openai";
const openai = new OpenAI();

const response = await openai.responses.create({
  model: "o3-mini",
  input: "What is the capital of France?"
});
console.log(response.output_text);
Migration Tip: If you're building anything new in 2026, start with the Responses API. Chat Completions still works but receives no new features.
⌨ HANDS-ON LABHit the Responses API with curl
⭐ +150 XP

Skip the SDK - talk to the Responses API raw. Set your key, then fire a real POST at /v1/responses with a Bearer token.

1Export your API key as the environment variable OPENAI_API_KEY (any value works in the sandbox).
2POST to https://api.openai.com/v1/responses with curl, authenticating via the Authorization: Bearer header.
lab-sandbox — simulated environment
INFINITY LAB SANDBOX v2.6 — simulated shell
Type the command for the current objective. Helpers: "hint", "solution", "clear".
$
OBJECTIVE 1 / 2 — type "hint" if stuck
SYNAPSE VERIFICATION
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What does the Responses API replace?
Only the Assistants API
Only Chat Completions
Both Chat Completions and the Assistants API as the primary development interface
The Embeddings API