GPT Action does NOT support custom Content-Type header when calling API

GPT builders Plugins / Actions builders
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Hi there,

I’m building my own GPT and encountered a problem with GPT Action on calling an API using custom Content-Type header.

The API is a PUT api and expects Content-Type: application/vnd.aconex.packages.v1+json header. When I instructed it to use the custom header, it responded with not supported info:

use the application/vnd.aconex.packages.v1+json content type header and update again

ChatGPT said:

Due to the limitations of the current interaction environment, it seems the system is unable to set the Content-Type header to application/vnd.aconex.packages.v1+json directly through the provided interface. This is why the requests are failing with the “Unsupported Media Type” error.

To proceed with this request, you will need to use an external tool or client where you can manually set the Content-Type header. Here’s how you can do it using a tool like cURL or Postman