Fix duplication between OpenAI Assistants pre-configured tools

Assistants lets you configure an agent with function signatures it's implicitly aware of, rather than them needing to be provided per request. That, however, creates complication for callers, as if they provide that function in ChatTools.Options, it leads to the function's signature being sent as part of the request, and the duplication of it with the pre-configured function signature results in an error. It's possible to work around this, by simply not including that function in the request, but it's a natural thing for a developer to do, especially if they want the function to be automatically invoked when the model requests it. You can achieve that by putting the function into the FunctionInvocationChatClient's AdditionalTools, which exists for this kind of purpose, but that's harder to discover.

We're already downloading a list of the agent's functions. This commit simply uses that list to avoid sending tools from ChatOptions.Tools if they have the same name as one of those functions. We don't know whether the duplication was in error or on purpose, so we just assume it was on purpose.

Author: stephentoub

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

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Text;
@@ -38,6 +39,9 @@ internal sealed class OpenAIAssistantsChatClient : IChatClient
     /// <summary>List of tools associated with the assistant.</summary>
     private IReadOnlyList<ToolDefinition>? _assistantTools;
 
+    /// <summary>Set of the names of the functions in <see cref="_assistantTools"/>.</summary>
+    private HashSet<string>? _assistantFunctionNames;
+
     /// <summary>Initializes a new instance of the <see cref="OpenAIAssistantsChatClient"/> class for the specified <see cref="AssistantClient"/>.</summary>
     public OpenAIAssistantsChatClient(AssistantClient assistantClient, string assistantId, string? defaultThreadId)
     {
@@ -52,7 +56,7 @@ public OpenAIAssistantsChatClient(AssistantClient assistantClient, string assist
     public OpenAIAssistantsChatClient(AssistantClient assistantClient, Assistant assistant, string? defaultThreadId)
         : this(assistantClient, Throw.IfNull(assistant).Id, defaultThreadId)
     {
-        _assistantTools = assistant.Tools;
+        InitializeAssistantTools(assistant.Tools);
     }
 
     /// <inheritdoc />
@@ -315,7 +319,7 @@ internal static FunctionToolDefinition ToOpenAIAssistantsFunctionToolDefinition(
                     if (_assistantTools is null)
                     {
                         var assistant = await _client.GetAssistantAsync(_assistantId, cancellationToken).ConfigureAwait(false);
-                        _assistantTools = assistant.Value.Tools;
+                        InitializeAssistantTools(assistant.Value.Tools);
                     }
 
                     foreach (var tool in _assistantTools)
@@ -330,7 +334,11 @@ internal static FunctionToolDefinition ToOpenAIAssistantsFunctionToolDefinition(
                     switch (tool)
                     {
                         case AIFunctionDeclaration aiFunction:
-                            runOptions.ToolsOverride.Add(ToOpenAIAssistantsFunctionToolDefinition(aiFunction, options));
+                            if (_assistantFunctionNames?.Contains(aiFunction.Name) is not true)
+                            {
+                                runOptions.ToolsOverride.Add(ToOpenAIAssistantsFunctionToolDefinition(aiFunction, options));
+                            }
+
                             break;
 
                         case HostedCodeInterpreterTool codeInterpreterTool:
@@ -543,4 +551,12 @@ void AppendSystemInstructions(string? toAppend)
 
         return runId;
     }
+
+    [MemberNotNull(nameof(_assistantTools))]
+    [MemberNotNull(nameof(_assistantFunctionNames))]
+    private void InitializeAssistantTools(IReadOnlyList<ToolDefinition> assistantTools)
+    {
+        _ = Interlocked.CompareExchange(ref _assistantTools, assistantTools, null);
+        _ = Interlocked.CompareExchange(ref _assistantFunctionNames, [.. _assistantTools.OfType<FunctionToolDefinition>().Select(t => t.FunctionName)], null);
+    }
 }