Best when you control the exact HTTP calls (useful for benchmarks):

1. Create a GPT → Configure → Actions.
2. Import from URL: https://guides.co/api/gdf/v1/openapi.json
3. Confirm servers shows https://guides.co/api/gdf/v1.
4. Authentication → API Key → header Authorization → Bearer {your_full_key}.
5. Paste Instructions for your AI from Studio.
6. Add a privacy policy URL (OpenAI requirement).

Test: "List my guides" → should call GET /catalog.