Looks great! I think this is a perfectly clear distinction between definition/implementation.

Thanks much for adding! The only other thing that may be nice to include is a simple helper / API to construct definitions for non-invokable tools (such as server-side tools).

Pull Request Overview

This PR splits AIFunction into a base class hierarchy by introducing AIFunctionDefinition as a new base class. The main purpose is to enable scenarios where function metadata is needed without invocability, allowing better separation of concerns between function definition and execution.

• Introduces AIFunctionDefinition as a base class containing only metadata properties (Name, Description, JsonSchema, ReturnJsonSchema)
• Updates AIFunction to inherit from AIFunctionDefinition while maintaining invocation capabilities
• Adds support for non-invocable function definitions in FunctionInvokingChatClient with new TerminateOnUnknownCalls property

Reviewed Changes

Copilot reviewed 34 out of 34 changed files in this pull request and generated 1 comment.

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Other than misgivings about the choice of name, this is a good change.