In Copilot Studio, custom connectors are the specific components responsible for connecting an AI agent to external APIs. While standard connectors exist for common services, custom connectors allow developers to define a wrapper around any REST API. This wrapper specifies the API's host, base path, operations (e.g., GET, POST), parameters, and authentication methods. Once created, the custom connector can be called from within a copilot's topic to interact with the external system, send data, and receive responses.

A. Topics define the conversation logic and can call a connector, but they are not the component that establishes the connection itself.

C. Variables are used to store and manage data within the copilot's memory during a conversation, not to connect to external systems.

D. Prompts are instructions for a generative AI model to generate content; they do not handle the technical connection to an API endpoint.

1. Microsoft Copilot Studio Documentation. (2024). Create and use custom connectors in Microsoft Copilot Studio. "If you have a web service or API that you want to connect to from your copilot, you need to create a custom connector... The custom connector defines the operations that the API can perform." Section: "Introduction".

2. Microsoft Power Platform Documentation. (2024). Custom connectors. "Custom connectors are a wrapper around a REST API that allows Power Automate, Power Apps, and Microsoft Copilot Studio to communicate with that REST API." Section: "Overview".

3. Microsoft Learn. (2024). Call an action in Microsoft Copilot Studio. "Actions in Microsoft Copilot Studio let you call reusable Power Platform components, such as... custom connectors, which allow you to connect to external systems and APIs." Section: "Overview of actions".