Help! Prompting Fine-Tuned Vector AI Model

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1

I’ve been troubleshooting N8N for hours now trying to get an http request to post a chat input to a fine-tuned Vector AI model I made, I keep getting errors like “Bad request - please check your parameters Invalid JSON payload received. Unknown name “”: Root element must be a message.”

Anyone go through this before?

2

Hey! That error usually points to an issue with how the JSON payload is structured for Vertex AI chat models. To help debug this quickly, could you share:

  1. What model are you using? (e.g. chat-bison, text-bison, or a fine-tuned variant?)
  2. What’s the exact JSON body you’re sending in the HTTP Request node?
  3. Are you using manual Bearer token auth or OAuth2 credentials in n8n?

With this, I can guide you to a working config. Looking forward to your reply!

Also try to give input in the format given below:

JSON File:

{
“instances”: [
{
“messages”: [
{
“author”: “user”,
“content”: {{$json[“chat_input”]}} // Replace with your chat input value
}
]
}
]
}