Can the Assistants API use OpenAPI-based actions instead of custom function calls?

The key difference is that while Custom GPTs let you define actions using an OpenAPI spec directly (making integration accessible without coding), the Assistants API focuses on custom functions via function calling.

For Custom GPTs

• Actions via OpenAPI: You can provide an OpenAPI specification to define endpoints.
• Non-Coding Advantage: This allows even non-coders to integrate external APIs by simply describing the API.

For the Assistants API

• Function Calling: It allows you to define custom function signatures that behave like our function calling feature.
• No Direct OpenAPI Specification: There isn’t an option to specify an OpenAPI spec directly (i.e., “Actions”) for an Assistant. Instead, you implement the external API call as a function in your code.

Bottom Line

If you're looking to have an Assistant use external APIs as a plug-and-play “action” defined solely by an OpenAPI spec, that capability isn’t currently available in the Assistants API. To achieve similar functionality, you would need to implement a function (i.e., use function calling) that makes the API call and handles the response. This is why for assistants, while you can create functions, you don't have the same direct OpenAPI-based Actions interface available as in Custom GPTs.