Can’t send image URLs to GPT-4o using External API Request – Params field won’t accept object

Answered

Hey Xano team + community — I’ve hit a wall trying to integrate OpenAI’s GPT-4o Vision model and could use your help.

I’m building an app where users upload two images (current hair and inspiration). I want to send those image URLs from Xano to OpenAI via an External API Request.

Here’s the issue:

The params field in the External API step only lets me input plain text. Even when I set it to object, it still shows a raw text editor — no way to enter proper JSON structure with arrays or nested objects.

I’ve:

  • Converted the endpoint to a Function Stack

  • Tried raw body mode (but the API doesn’t parse it correctly)

  • Attempted to re-add the request step clean

  • Followed every formatting rule I could find

Here’s the body I need to send:

{

"model": "gpt-4o",

"messages": [

{

"role": "system",

"content": "You are a professional hair colorist helping stylists match formulas based on client hair and inspiration photos."

},

{

"role": "user",

"content": [

{

"type": "text",

"text": "Based on this client's current hair and inspiration photo, provide a hair color formula using professional brands."

},

{

"type": "image_url",

"image_url": { "url": "https://example.com/current.jpg" }

},

{

"type": "text",

"text": "Here is the desired look:"

},

{

"type": "image_url",

"image_url": { "url": "https://example.com/inspo.jpg" }

}

]

}

]

}

How can I send this JSON object properly through Xano’s External API Request?

Do I need to use a raw request workaround or custom proxy? Or is there a cleaner way to enable full JSON support?

Would love to hear from anyone who’s used OpenAI Vision or sent structured objects like this.

Thanks in advance!

4 replies