Versatility of APIs (response, assistant, agents)

Community
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is there some tutorial or could somebody pls explain what is the key differences and use cases for:

  • Assistant API
  • Response API
  • OpenAI Agents SDK
2

I asked ChatGPT and mostly agree! :wink:

  • Assistants API (v2)
  • Status: Beta, supported through ~H2 2026 (deprecation announced H1 2026) OpenAI Platform
  • When to use: Short-term “hosted” assistants with built-in state (+ threads) and tools (file_search, code interpreter).
  • Responses API
  • Status: GA, new primary endpoint for chat + tools + state persistence OpenAI Community
  • When to use: New projects needing fastest, most flexible chat + function-/tool-calling without rolling your own history.
  • OpenAI Agents SDK
  • Status: Open-source Python/Node framework on top of Responses/Chat Completions
  • When to use: Building complex, multi-agent workflows with orchestration, guardrails, and observability.

Have you started with the Quickstart guide?

The Cookbook (and this forum) are super helpful too.

What are you trying to build?

3

thank you Paul!
I was going through OpenAI Platform docs quickly, just wanted to grasp the abilities of the tools.
a little bit lost because I saw a kinda the same things in every API (models, instructions, tools) and that’s why was confused about application scopes of these APIs.
I am not coding anything with OpenAI APIs, just some self-education in order to have idea what is going on

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Hey but what about Completions endpoint :slight_smile:

I’m still using it (and I presume it will basically never go away since it’s the most basic endpoint) and I find it to be the most powerful in my use case because of complete control of the context window and output processing without any complexity or routing from openAI…

I.e. To me the completions end point is communicating the most directly with the LLM itself.

Of course for all the I/O processing, agents, RAG, etc. you have to build your own system… but hey just wanted to give a +1 for what is maybe “old school” now :slight_smile:

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Completions is still way faster than others, easily 2x the responses API

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Assistants API: obsolete (end-of-life next year)

Responses API: low-level (but powerful) API that lets you generate a single response at a time using some convenient built-in tools (such as file_search, web_search, code_interpreter) and your own custom tools. You have full control over prompts and all parameters, etc. We use it for a RAG-based expert system, but you can do almost anything with it.

Agents SDK: This is a much higher-level set of tools for building AI applications. Powerful but designed with certain specific purposes. Will save you some time if you need something really complex that fits within the concepts that they are targeting.

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