How to Use the “Create an Action” Feature in Custom GPTs

Turn your GPT into a powerful API-aware assistant that can fetch data, trigger services, or complete tasks — all from inside the chat.

TL;DR — What You Need To Know

• “Actions” let your custom GPT interact with external APIs — think booking systems, CRMs, weather lookups or internal databases
• You define the API, describe it with an OpenAPI schema, and explain when and how the GPT should use it
• Ideal for businesses that want to automate workflows inside ChatGPT — without needing full app builds
• Common use cases across Asia include: order lookups, stock checks, HR systems, and appointment scheduling
• This guide walks you through building, testing, and deploying your first Action step by step

What Is a GPT Action?

Actions allow your GPT to call an external API endpoint during a conversation. For example:

“Can you check the current air quality in Jakarta?”
→ GPT sends a request to an API you defined
→ Returns real-time AQI data into the chat

This means your GPT isn’t just a static assistant — it becomes a live, interactive tool that can “do” things.

Step 1: Set Up Your Custom GPT

Start as usual:

• Go to: https://chat.openai.com/gpts
• Click “Create”
• Fill out your GPT’s name, instructions, and tone as needed
• Switch to the Configure tab

Step 2: Prepare Your API

You’ll need an existing web API to connect. This could be:

• A public API (like OpenWeather, Google Calendar, etc.)
• A private internal API (e.g., inventory, HR systems, internal bots)
• A no-code tool like Zapier or Make, which exposes endpoints

Make sure:

• It supports HTTPS
• It accepts and returns JSON
• You have the API key (if it requires auth)

Example Use Case:
Check a user’s leave balance via an HR API.

Step 3: Write Your OpenAPI Schema

This is how GPT knows what your API does. You describe it using the OpenAPI 3.0 format — a structured YAML or JSON file.

Here’s a simple example for a GET request to check leave days:

yamlCopyEditopenapi: 3.0.0
info:
  title: HR API
  version: 1.0.0
paths:
  /leave-balance:
    get:
      summary: Check user's leave balance
      parameters:
        - in: query
          name: employee_id
          schema:
            type: string
          required: true
          description: ID of the employee
      responses:
        '200':
          description: Leave balance returned
          content:
            application/json:
              schema:
                type: object
                properties:
                  remaining_days:
                    type: integer

Paste this into an .yaml file or host it on a public URL (e.g., via GitHub Gist or a secure S3 bucket).

Step 4: Add the Action in GPT Builder

Back in the Configure tab:

1. Scroll to “Actions”
2. Click “Add Action”
3. Paste your API’s base URL
4. Paste or link to your OpenAPI schema
5. Add a description for GPT — e.g., “Use this action to check leave balances when users ask about time off”
6. Set authentication:
   • No auth
   • API key (via headers or query param)
   • OAuth (advanced)

Once added, test the schema using GPT’s built-in validator.

Step 5: Write GPT Instructions to Use the Action

Update your GPT’s Instructions to explicitly describe when to use the action.

Example:

When a user asks about leave days, use the HR API to check their balance. Ask for their employee ID first. Do not guess.

This ensures GPT won’t try to call the API unless it’s appropriate.

Step 6: Test the Action

Switch to Preview GPT and type:

“How many leave days do I have left?”
→ GPT should ask for your employee ID
→ Then call the action
→ Then return the result, e.g. “You have 12 leave days remaining.”

Watch for:

• Correct input formatting
• Unexpected errors or failed calls
• GPT failing to use the action when it should

Fix instructions or the schema if anything breaks.

Step 7: Publish and Maintain

Once you’re confident:

• Hit Publish
• Choose Private, Link or Public visibility
• Keep your API uptime in mind — if the endpoint is down, GPT won’t function properly
• Monitor logs and rate limits if it’s a high-traffic GPT

Real-World Examples from Asia

• Singapore travel agencies integrating visa APIs for instant eligibility checks
• Malaysian e-commerce startups checking stock or delivery status via GPT
• Indonesian HR tech firms adding internal policy lookups via GPTs
• Thai insurance brokers offering premium calculators through live API calls

The best part? You can connect more than one action — allowing your GPT to call several services like a digital command centre.

Security Note

Always hide API keys and use headers or environment variables for private services. GPTs do not store user data, but you are responsible for how your API handles it.

Avoid exposing endpoints with write access (like deleting records or submitting payments) unless fully secured and monitored.

Final Thoughts: ChatGPT as Your API Concierge

With Actions, GPTs are no longer just helpful assistants — they’re functional bridges into your real systems. In Asia, where lean automation is everything, this may be the most powerful GPT feature yet.

Whether you’re triggering a report, checking a shipment, or logging a support ticket — if there’s an API for it, GPT can now do it.

So the question becomes: what internal service would you automate first?

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