Tool reduction

[MackinnonBuck]

Summary

This draft introduces the tool reduction feature set:

• New abstractions (IToolReductionStrategy) for selecting a subset of tools per request.
• Middleware (ToolReducingChatClient) that applies a configured strategy automatically.
• An initial embedding-based implementation (EmbeddingToolReductionStrategy) as a first strategy.
• Supporting builder extensions and tests.

All components are marked experimental and may evolve. Additional strategies can be added in follow-up work.

Next Steps

• Additional tool reduction strategy implementations.
• Refinements to abstractions as necessary.

Feedback welcome before expanding scope.

Fixes #6670

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull Request Overview

This PR introduces a tool reduction feature set for managing large tool catalogs in AI chat applications. The feature allows for automatically selecting a subset of tools per request using configurable strategies.

Key changes:

• New abstractions for tool reduction strategies with an embedding-based implementation
• Middleware that automatically applies tool reduction to chat requests
• Comprehensive test coverage including integration tests across different scenarios

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Libraries/Microsoft.Extensions.AI.Abstractions/ToolReduction/IToolReductionStrategy.cs	Defines the core abstraction interface for tool reduction strategies
src/Libraries/Microsoft.Extensions.AI/ToolReduction/EmbeddingToolReductionStrategy.cs	Implements embedding-based tool selection using similarity scoring
src/Libraries/Microsoft.Extensions.AI/ToolReduction/ToolReducingChatClient.cs	Middleware client that applies tool reduction before delegating to inner client
src/Libraries/Microsoft.Extensions.AI/ToolReduction/ChatClientBuilderToolReductionExtensions.cs	Extension methods for integrating tool reduction into chat client pipelines
test/Libraries/Microsoft.Extensions.AI.Integration.Tests/ToolReductionTests.cs	Comprehensive unit and integration tests for tool reduction functionality
test/Libraries/Microsoft.Extensions.AI.Integration.Tests/ChatClientIntegrationTests.cs	Integration tests demonstrating real-world tool reduction scenarios
test/Libraries/Microsoft.Extensions.AI.OpenAI.Tests/OpenAIChatClientIntegrationTests.cs	Adds embedding generator support for OpenAI integration tests
src/Libraries/Microsoft.Extensions.AI/Microsoft.Extensions.AI.csproj	Adds System.Numerics.Tensors dependency for embedding similarity calculations
eng/packages/General.props	Moves System.Numerics.Tensors to general packages from test-only
eng/packages/TestOnly.props	Removes System.Numerics.Tensors from test-only packages

Comments suppressed due to low confidence (2)

src/Libraries/Microsoft.Extensions.AI/ToolReduction/EmbeddingToolReductionStrategy.cs:1

• This method exceeds 120 characters per line. Consider breaking the parameter list across multiple lines for better readability.

// Licensed to the .NET Foundation under one or more agreements.

src/Libraries/Microsoft.Extensions.AI/ToolReduction/EmbeddingToolReductionStrategy.cs:1

• This method exceeds 120 characters per line. Consider breaking the parameter list across multiple lines for better readability.

// Licensed to the .NET Foundation under one or more agreements.

[ericstj]

Looks good to get out there and get feedback.

I think this will still only expose a subset of the tools to the model, with no way for the model to page in the rest - but I suppose that's by design for this implementation.