Step-by-Step Guide to Creating Custom GPTs with Knowledge and Action Plugins

GPTs are custom versions of ChatGPT that anyone can create without any coding. They can be tailored for daily life, specific tasks, work, or family use, and can be shared with others.

This tutorial provides a complete, hands‑on walkthrough for building a nutrition‑analysis GPT (named “Nutri Buddy”). It starts with logging into the new ChatGPT interface, clicking “Explore”, and selecting “Create a GPT”. The creation process is dialog‑based, allowing you to describe the GPT’s purpose, name, avatar, and actions.

The guide explains how to configure the GPT’s knowledge base by uploading files such as PDFs or Word documents, enabling the model to retrieve professional information from these sources.

It also covers the Action (custom plugin) feature, which lets the GPT call external APIs. As an example, the tutorial shows how to integrate the Boohee food database to retrieve calorie, protein, and carbohydrate information for a given food item, and then generate corresponding exercise suggestions.

Key configuration steps include specifying the URL and description for the API, defining the request schema, and mapping parameters extracted from the search URL. The full OpenAPI JSON configuration for the Action is provided below.

{
  "openapi": "3.1.0",
  "info": {
    "title": " Get Food Nutrition Data ",
    "description": "Retrieves current weather data for a location.",
    "version": "v1.0.0"
  },
  "servers": [
    {
      "url": " https://api.boohee.com"
    }
  ],
  "paths": {
    "/food/search": {
      "get": {
        "description": "Get nutrition information for a specific food item",
        "operationId": "GetFoodNutrition",
        "parameters": [
          {
            "name": "keyword",
            "in": "query",
            "description": " The name of the food item to retrieve nutrition information for ",
            "required": true,
            "schema": {
              "type": "string"
            }
          }
        ],
        "deprecated": false
      }
    }
  },
  "components": {
    "schemas": {}
  }
}

After configuring the GPT, you can save and publish it with visibility options: private, link‑only, or public (the latter requires domain DNS verification). The article notes that with the upcoming GPT Store, more developers will create and monetize GPTs, turning ChatGPT into a platform for both users and creators.