blog-05-chatgpt-custom-gpt

Deploy Your AI Agent as a ChatGPT Custom GPT

Hey there,

Your Second Brain OS agent is configured and your tools are live. Now let's make it available inside ChatGPT. By the end of this guide, you (or your customers) will be able to interact with your AI agent through ChatGPT's familiar interface — with full access to your tools, knowledge, and skills.

This is particularly useful if you want to:

• Use your agent internally (you and your team interact with it inside ChatGPT)
• Offer your agent to customers who already have ChatGPT accounts
• Give clients a familiar interface without building a website or setting up voice

What You'll Need

• A ChatGPT Plus or Teams account (Custom GPTs require a paid plan)
• Your Second Brain OS account (setup completed from the main guide)
• Your SBOS API key (available from your SBOS dashboard)

How Custom GPTs Work with SBOS

Custom GPTs don't support MCP servers directly. Instead, they use something called Actions — which are API endpoints defined by an OpenAPI schema.

Quick clarification: "OpenAI" (the company that makes ChatGPT) and "OpenAPI" (a standard format for describing API endpoints) are two completely different things that happen to have almost identical names. OpenAPI is an industry standard — it has nothing to do with OpenAI the company. ChatGPT uses the OpenAPI standard to understand what tools are available and how to call them. SBOS generates this schema for you automatically, turning all your public tools into Actions that ChatGPT can call.

If you're a business owner: Think of it this way — ChatGPT is like a really smart assistant, but out of the box it can't access your calendar, your CRM, or your business data. Actions are the "permissions" that give it access. SBOS generates these permissions for you in one click.

If you've used Zapier or n8n: If you've ever used "Zapier Actions" inside a Custom GPT, this is the same pattern. You're giving ChatGPT a set of API endpoints it can call. The difference is that these endpoints are your actual SBOS tools (booking, CRM, knowledge search, etc.) rather than Zapier triggers.

Step 1: Generate Your OpenAPI Schema

1. Go to secondbrainos.com/open-ai-custom-gpts
2. Click the button to generate your OpenAPI schema
3. This creates a schema containing all your public SBOS tools — formatted exactly how ChatGPT expects
4. Copy the generated schema (you'll paste it in the next step)

The schema tells ChatGPT: "Here are the tools available, here's what each one does, here are the parameters it expects, and here's where to send the request." You don't need to write any of this yourself — SBOS generates it from your existing tool configuration.

Step 2: Create Your Custom GPT

1. Go to chatgpt.com
2. Click Explore GPTs (in the sidebar) → Create (top right)
3. Click the Configure tab (not the conversational "Create" tab)

Fill in the following:

Name — Give your Custom GPT a name that matches your business (e.g. "Acme Booking Assistant", "Sarah - Virtual Receptionist", "My Business AI Agent")

Description — A short sentence about what it does (e.g. "Book, reschedule, and cancel appointments. Check availability and answer questions about our services.")

Instructions — This is the system prompt. You can copy the exact same system prompt from your SBOS profile (Profile → AI Agent Settings → auto_responder_instructions). This ensures your Custom GPT behaves identically to your agent on other channels.

If you're a business owner: The instructions field is like the training script you'd give a new hire. It tells the AI how to behave, what tone to use, and what to do in different situations. Since you've already written this for your SBOS agent, you can just copy it over.

Step 3: Add Your Tools as Actions

1. Scroll down to Actions and click Create new action
2. In the Schema field, paste the OpenAPI schema you generated in Step 1
3. Under Authentication:
   • Select API Key
   • Auth Type: Bearer
   • Paste your full Second Brain OS API key (the complete value including Bearer, e.g. Bearer rec1tty51WZwjrDoe:022d917a-c134-705e-b310-393298493)

If you've used Zapier Actions in Custom GPTs: This is the same flow — you're adding an API endpoint and authenticating it. The only difference is the schema comes from SBOS instead of Zapier, and the tools map directly to your business operations.

Step 4: Configure the Model

1. Back in the Configure tab, scroll to the Model dropdown
2. Select your preferred GPT model (e.g. GPT-4o or the latest available)
3. This is the model ChatGPT will use to process conversations — it works alongside your SBOS tools

Step 5: Save & Publish

1. Click Save in the top right
2. Choose your publishing option:
   • Only me — for personal/internal use
   • Anyone with a link — share with specific people (recommended for clients)
   • Everyone — list publicly in the GPT Store
3. Click Confirm

You'll get a shareable link (e.g. chatgpt.com/g/g-abc123-your-agent). Share this with anyone who should have access.

Step 6: Test Your Custom GPT

1. Open your Custom GPT from the link or from My GPTs in the sidebar
2. Test the full workflow — try whatever your agent is designed to handle:
   • "What times are available this week?"
   • "Book me in for Thursday at 2pm"
   • "Search my knowledge base for pricing information"
3. ChatGPT will show you when it's calling an Action (your SBOS tools) — you'll see the tool name and a brief summary of what it's doing

If you're a business owner: The first time ChatGPT calls one of your tools, it may ask you to confirm ("Allow this action?"). Click Always allow so it works smoothly going forward.

How It Works Under the Hood

1. You (or a customer) chats with the Custom GPT in ChatGPT's interface
2. ChatGPT processes the conversation using the GPT model and your system prompt
3. When it needs to take an action (book, search, cancel, etc.), it calls the SBOS API endpoint defined in your OpenAPI schema
4. SBOS authenticates the request using your API key, executes the tool, and returns the result
5. ChatGPT incorporates the result into its response

Your SBOS tools run server-side. ChatGPT never has direct access to your Calendly, CRM, or any external service — it goes through SBOS, which handles authentication and execution securely.

Keeping Your Custom GPT in Sync

When you add new tools to your SBOS account or change tool visibility, your Custom GPT won't automatically pick up those changes. To update:

1. Go to secondbrainos.com/open-ai-custom-gpts and regenerate the schema
2. Edit your Custom GPT → Actions → replace the old schema with the new one
3. Save

This only applies when your tool inventory changes — your knowledge base updates flow through automatically and can be accessed via the searchMyKnowledge action.

Troubleshooting

Your AI agent is now live inside ChatGPT. Anyone with the link can interact with it using ChatGPT's familiar interface — and it has full access to the same tools powering your website chat, voice agent, and Telegram bot.

Next up: check out the other channel deployment guides:

• Website chat widget (ChatKit)
• Voice AI (ElevenLabs)
• WhatsApp, Instagram, Website & Telegram
• Claude Desktop & Claude Code
• CLI & Agent URL