[Pasindu Madusha (epcm18)]

Motivation & Context

InstructionBuilder.BuildExecuteCodeDescription in Microsoft.Agents.AI.LocalCodeAct listed each host AIFunction name and description but never read JsonSchema, so models could not learn parameter names, requiredness, descriptions, enums, or nested shapes for call_tool(...). This is the LocalCodeAct counterpart of #8446 / #8528. The Python fix (#8459) covered both of its runtimes; this PR brings the second .NET runtime in line.

Description & Review Guide

• What are the major changes?
  • BuildExecuteCodeDescription appends each host tool's existing JsonSchema under Parameters (JSON Schema): when the schema describes properties, emits Parameters: none. for zero-argument tools, and stays silent for unconstrained schemas ({} or boolean roots). This is the same rendering and the same guards as .NET: include host-tool JsonSchema in Hyperlight execute_code descriptions #8528 so both .NET packages produce identical descriptions.
  • Regression coverage: parameterized tool, zero-parameter tool, and unconstrained schema in InstructionBuilderTests; description and code-only input schema assertions for both LocalExecuteCodeFunction (new test class) and LocalCodeActProvider.
  • README documents the behaviour, the model-visibility caveat for parameter metadata, and the JsonStringEnumConverter note for enums.
• What is the impact of these changes? No public API changes. The execute_code input schema remains the single code parameter. No-tool output, approval behavior, and file-mount instructions are unchanged.
• What do you want reviewers to focus on?
  • The rendering intentionally mirrors .NET: include host-tool JsonSchema in Hyperlight execute_code descriptions #8528. If maintainers choose a different format there, I will match it here.
  • The schema block is duplicated between the Hyperlight and LocalCodeAct builders because the packages share only Abstractions. Happy to move both into a src/Shared injected source file as a follow-up once .NET: include host-tool JsonSchema in Hyperlight execute_code descriptions #8528 lands.
  • A compact vs json format option like Python's tool_description_format is deliberately out of scope; I can open a separate design issue for both packages if wanted.

Related Issue

Fixes #8775
Partially addresses: #8446 #8125

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR is linked to an issue and there is no other open PR for this issue (see Related Issue above).
• This is not a breaking change.

Evidence

• Old red: BuildExecuteCodeDescription_WithToolParameters_IncludesParameterMetadata fails on main (no parameter metadata in the description).
• New green: dotnet test --project tests/Microsoft.Agents.AI.LocalCodeAct.UnitTests/Microsoft.Agents.AI.LocalCodeAct.UnitTests.csproj -f net10.0 → 109/109 passed.

[Copilot]

Copilot review overview

🟡 Changes recommended

The new C# test file violates the repository’s required UTF-8 BOM encoding convention.

Review effort: Balanced
Findings: 1

Open (1)

• Add UTF-8 BOM to new C# file · New

What changed in this PR

Exposes host-tool JSON schemas in .NET LocalCodeAct descriptions while preserving the code-only execution schema.

Changes:

• Renders parameter schemas and zero-parameter status.
• Adds regression tests for both entry points.
• Documents schema visibility and enum handling.

File	Description
Internal/​InstructionBuilder.cs	Adds host-tool schema rendering.
README.md	Documents parameter metadata exposure.
InstructionBuilderTests.cs	Tests schema rendering cases.
LocalExecuteCodeFunctionTests.cs	Tests standalone function behavior.
LocalCodeActProviderTests.cs	Tests provider-generated function behavior.

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[Pasindu Madusha (epcm18)]

@microsoft-github-policy-service agree

[Pasindu Madusha (epcm18)]

Hi Eduard van Valkenburg (@eavanvalkenburg) , a gentle ping when you have a moment: this is the .NET counterpart of microsoft/agent-framework#8459. Would you be able to go through the changes and check whether they match? Could you also approve the workflow runs here and on microsoft/agent-framework#8528? Thanks!