Add marker AITool for enabling code interpreters

Various AI services (Gemini, Bedrock, OpenAI, etc.) now support server-side code interpreting, where the model can generate code it can then execute in a sandbox. For good reason, they all require opting in. We can model that well as an AITool-derived type.

Author: stephentoub

src/Libraries/Microsoft.Extensions.AI.Abstractions/CodeInterpreterTool.cs

@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.Extensions.AI;
+
+/// <summary>Represents a tool that can be specified to an AI service to enable it to execute code it generates.</summary>
+/// <remarks>
+/// This tool does not itself implement code interpration. It is a marker that can be used to inform a service
+/// that the service is allowed to execute its generated code if the service is capable of doing so.
+/// </remarks>
+public class CodeInterpreterTool : AITool
+{
+    /// <summary>Initializes a new instance of the <see cref="CodeInterpreterTool"/> class.</summary>
+    public CodeInterpreterTool()
+    {
+    }
+
+    /// <summary>Gets or sets additional properties that impact the behavior of the tool.</summary>
+    public AdditionalPropertiesDictionary? AdditionalProperties { get; set; }
+}

src/Libraries/Microsoft.Extensions.AI.OpenAI/OpenAIAssistantClient.cs

@@ -212,27 +212,38 @@ private static (RunCreationOptions RunOptions, List<FunctionResultContent>? Tool
             {
                 foreach (AITool tool in tools)
                 {
-                    if (tool is AIFunction aiFunction)
+                    switch (tool)
                     {
-                        bool? strict =
-                            aiFunction.Metadata.AdditionalProperties.TryGetValue("Strict", out object? strictObj) &&
-                            strictObj is bool strictValue ?
-                            strictValue : null;
-
-                        var functionParameters = BinaryData.FromBytes(
-                            JsonSerializer.SerializeToUtf8Bytes(
-                                JsonSerializer.Deserialize(aiFunction.Metadata.Schema, OpenAIJsonContext.Default.OpenAIChatToolJson)!,
-                                OpenAIJsonContext.Default.OpenAIChatToolJson));
-
-                        runOptions.ToolsOverride.Add(ToolDefinition.CreateFunction(aiFunction.Metadata.Name, aiFunction.Metadata.Description, functionParameters, strict));
+                        case AIFunction aiFunction:
+                            bool? strict =
+                                aiFunction.Metadata.AdditionalProperties.TryGetValue("Strict", out object? strictObj) &&
+                                strictObj is bool strictValue ?
+                                strictValue : null;
+
+                            var functionParameters = BinaryData.FromBytes(
+                                JsonSerializer.SerializeToUtf8Bytes(
+                                    JsonSerializer.Deserialize(aiFunction.Metadata.Schema, OpenAIJsonContext.Default.OpenAIChatToolJson)!,
+                                    OpenAIJsonContext.Default.OpenAIChatToolJson));
+
+                            runOptions.ToolsOverride.Add(ToolDefinition.CreateFunction(aiFunction.Metadata.Name, aiFunction.Metadata.Description, functionParameters, strict));
+                            break;
+
+                        case CodeInterpreterTool:
+                            runOptions.ToolsOverride.Add(ToolDefinition.CreateCodeInterpreter());
+                            break;
                     }
                 }
             }
 
             // Store the tool mode.
             switch (options.ToolMode)
             {
+                case NoneChatToolMode:
+                    runOptions.ToolConstraint = ToolConstraint.None;
+                    break;
+
                 case AutoChatToolMode:
+                case null:
                     runOptions.ToolConstraint = ToolConstraint.Auto;
                     break;
 

test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/CodeInterpreterToolTests.cs

@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Xunit;
+
+namespace Microsoft.Extensions.AI;
+
+public class CodeInterpreterToolTests
+{
+    [Fact]
+    public void Constructor_Roundtrips()
+    {
+        var tool = new CodeInterpreterTool();
+        Assert.Null(tool.AdditionalProperties);
+
+        var props = new AdditionalPropertiesDictionary();
+        tool.AdditionalProperties = props;
+        Assert.Same(props, tool.AdditionalProperties);
+    }
+}