OpenAI responses API adapter for LLM and AI agent workflows

This n8n template demonstrates how to use OpenAI's Responses API with existing LLM and AI Agent nodes.

Though I would recommend just waiting for official support, if you're impatient and would like a round-about way to integrate OpenAI's responses API into your existing AI workflows then this template is sure to satisfy!

This approach implements a simple API wrapper for the Responses API using n8n's builtin webhooks. When the base url is pointed to these webhooks using a custom OpenAI credential, it's possible to intercept the request and remap for compatibility.

How it works

• An OpenAI subnode is attached to our agent but has a special custom credential where the base_url is changed to point at this template's webhooks.
• When executing a query, the agent's request is forwarded to our mini chat completion workflow.
• Here, we take the default request and remap the values to use with a HTTP node which is set to query the Responses API.
• Once a response is received, we'll need to remap the output for Langchain compatibility. This just means the LLM or Agent node can parse it and respond to the user.
• There are two response formats, one for streaming and one for non-streaming responses.

How to use

• You must activate this workflow to be able to use the webhooks.
• Create the custom OpenAI credential as instructed.
• Go to your existing AI workflows and replace the LLM node with the custom OpenAI credential. You do not need to copy anything else over to the existing template.

Requirements

• OpenAI account for Responses API

Customising this workflow

• Feel free to experiment with other LLMs using this same technique!
• Keep up to date with the Responses API announcements and make modifications as required.