Persistant JSON payload error with Printify draft via HTTP node

[Roland_Brandt]

Hello,

I’m experiencing a persistent issue when trying to create a Printify product draft from n8n. Despite multiple payload configurations and simplified workflows, I keep getting this error:

pgsql

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NodeOperationError: JSON parameter needs to be valid JSON
Node: HTTP Request (Create Printify Product Draft)
Node version: 4.2
n8n version: 1.91.3 (Cloud)

What I’m Trying to Do:

Send a POST request to https://api.printify.com/v1/shops/{shop_id}/products.json to create a product draft from data prepared in previous workflow steps (Vaultsmith quote + product info).

Minimal Workflow That Still Fails:

• Manual Trigger
• Code Node (builds static JSON payload)
• HTTP Request Node (POST to Printify, Body set to JSON)

Code Node Output (simplified hardcoded test):

json

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{
  "title": "Test Product – Hardcoded",
  "description": "This is a working test description.",
  "blueprint_id": 5,
  "print_provider_id": 99,
  "variants": [
    {
      "id": 17390,
      "price": 1999,
      "is_enabled": true
    }
  ],
  "print_areas": [
    {
      "variant_ids": [17390],
      "placeholders": {
        "front": {
          "images": [
            {
              "id": "
              "x": 0,
              "y": 0,
              "scale": 1,
              "angle": 0
            }
          ],
          "position": "front"
        }
      }
    }
  ]
}

HTTP Node Settings:

• Method: POST
• Body Content: JSON
• Body: {{$json}}
• Content-Type: application/json
• Auth: Bearer token (Printify API key)

What I’ve Tried:

• Building payload via Set node (JSON + expressions).
• Building payload via Code node (hardcoded + dynamic).
• Switching between Raw JSON and JSON parameter modes.
• Wrapping payload in JSON.stringify() and sending as Raw.
• Isolating this to a 3-node test workflow with no other dependencies.

Result:

All attempts return the same error:
NodeOperationError: JSON parameter needs to be valid JSON
This happens even with fully static, hardcoded payloads.

---

My Question:

• Is there a specific way the n8n HTTP Request node needs to be configured to POST a complex JSON payload like this?
• Could there be a bug in how n8n handles nested arrays/objects in JSON mode?
• Any working examples of posting complex nested JSON to an API like Printify would be appreciated.

Thank you for your help.

—
Roland Brandt

[jabbson]

Hey @Roland_Brandt hope all is well.

When I try this

I do not get error about JSON parameter needs to be valid JSON, I get authentication error (which happens after json validation). Are does this example work for you if you add your credentials?

[Roland_Brandt]

Thanks for checking this, Jabbson!

That’s really helpful to know it passes JSON validation on your end. I’ll double‑check my HTTP node authentication again — I’m using Bearer token auth with my Printify API key, but maybe something is off there. I’ll test using manual headers as you suggested and report back.

— Roland