Invalid endpoint URL error in creating action in GPTs to connect API

I am trying to create an action in GPT to connect to openai api to create an assistant. In a way when I ask GPT to create and assistant, creates one with openai api.

this is my schema:

info:
  title: OpenAI API
  version: "1.0.0"

servers:
  - url: https://api.openai.com/v1

paths:
  /assistants:
    post:
      operationId: createAssistants
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                model:
                  type: string
                  description: "ID of the model to use. You can use the List models API to see all of your available models, or see our Model overview for descriptions of them."
              required:
                - model
      responses:
        201:
          description: Assistant created
          content:
            application/json:
              schema:
                type: object
                properties:
                  id:
                    type: string
                  object:
                    type: string
                  created_at:
                    type: integer
                  model:
                    type: string
                  tools:
                    type: array
                    items:
                      type: object
                      properties:
                        type:
                          type: string
                required:
                  - id
                  - object
                  - created_at
                  - model
                  - tools

components:
  schemas: {}
  securitySchemes:
    ApiKeyAuth:
      type: http
      scheme: "bearer"

security:
  - ApiKeyAuth: []

And I always get this error:

{
  "response_data": {
    "error": {
      "message": "Invalid URL (POST /v1/assistants)",
      "type": "invalid_request_error",
      "param": null,
      "code": null
    }
  },
  "status_code": 404,
  "action_id": "g-075f77c3d4247b6c2249d63423f9a5"
}

While this is correct:

POST https://api.openai.com/v1/assistants

How can I solve it? Is this beacuse I am using OpenAI api in another openAI tool or it has another reason.

How can I add this header in schema:

OpenAI-Beta: assistants=v1

I tried this but does not work.

paths:
  /assistants:
    post:
      operationId: createAssistants
      parameters:
        - name: OpenAI-Beta
          in: header
          required: true
          schema:
            type: string
          example: assistants=v1```
I really appreciate your help.