feat: implement tool call

src/AnthropicClient/AnthropicApiClient.cs

@@ -82,6 +82,12 @@ public class AnthropicApiClient : IAnthropicApiClient
     }
 
     var chatResponse = Deserialize<ChatResponse>(responseContent) ?? new ChatResponse();
+    
+    if (request.Tools is not null && request.Tools.Count > 0)
+    {
+      chatResponse.ToolCall = GetToolCall(chatResponse, request.Tools);
+    }
+    
     return AnthropicResult<ChatResponse>.Success(chatResponse, anthropicHeaders);
   }
 
@@ -190,6 +196,11 @@ public class AnthropicApiClient : IAnthropicApiClient
           Usage = newUsage,
           Content = chatResponse.Content,
         };
+
+        if (request.Tools is not null && request.Tools.Count > 0)
+        {
+          chatResponse.ToolCall = GetToolCall(chatResponse, request.Tools);
+        }
       }
 
       // yield chat response on message stop
@@ -228,6 +239,25 @@ public class AnthropicApiClient : IAnthropicApiClient
     } while (true);
   }
 
+  private ToolCall? GetToolCall(ChatResponse response, List<Tool> tools)
+  {
+    var toolUse = response.Content.OfType<ToolUseContent>().FirstOrDefault();
+
+    if (toolUse is null)
+    {
+      return null;
+    }
+
+    var tool = tools.FirstOrDefault(t => t.Name == toolUse.Name);
+
+    if (tool is null)
+    {
+      return null;
+    }
+
+    return new ToolCall(tool, toolUse);
+  }
+
   private async Task<HttpResponseMessage> SendRequestAsync(MessageRequest request)
   {
     var requestContent = new StringContent(Serialize(request), Encoding.UTF8, JsonContentType);

src/AnthropicClient/Models/ChatResponse.cs

@@ -48,4 +48,10 @@ public class ChatResponse
   /// Gets the contents of the chat response.
   /// </summary>
   public List<Content> Content { get; init; } = [];
+
+  /// <summary>
+  /// Gets the tool call of the chat response. If the chat response does not contain a tool call, this property is null.
+  /// </summary>
+  [JsonIgnore]
+  public ToolCall? ToolCall { get; set; } = null;
 }

src/AnthropicClient/Models/ToolCall.cs

@@ -1,3 +1,8 @@
+using System.Reflection;
+using System.Text.Json;
+
+using AnthropicClient.Json;
+
 namespace AnthropicClient.Models;
 
 /// <summary>
@@ -5,13 +10,112 @@ namespace AnthropicClient.Models;
 /// </summary>
 public class ToolCall
 {
-  // TODO: Implementation
+  /// <summary>
-  // - each tool call needs parameters
+  /// Gets the tool of the tool call.
-  // - each tool call needs a tool name
+  /// </summary>
-  // - each tool needs function to call
+  public Tool Tool { get; }
-  // - tool may or may not need an instance
+
-  // - tool call will be given input from tool use
+  /// <summary>
-  // - tool call should have list of known functions
+  /// Gets the tool use of the tool call.
-  // - tool call should be able to find function by name
+  /// </summary>
-  // - tool call should be able to translate input to function parameters
+  public ToolUseContent ToolUse { get; }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="ToolCall"/> class.
+  /// </summary>
+  /// <param name="tool">The tool of the tool call.</param>
+  /// <param name="toolUse">The tool use of the tool call.</param>
+  /// <returns>A new instance of the <see cref="ToolCall"/> class.</returns>
+  public ToolCall(Tool tool, ToolUseContent toolUse)
+  {
+    Tool = tool;
+    ToolUse = toolUse;
+  }
+
+  /// <summary>
+  /// Invokes the tool call.
+  /// </summary>
+  /// <returns>The result of the tool call as an instance of <see cref="ToolCallResult{T}"/>.</returns>
+  public async Task<ToolCallResult<object>> InvokeAsync()
+  {
+    return await InvokeAsync<object>();
+  }
+
+  /// <summary>
+  /// Invokes the tool call.
+  /// </summary>
+  /// <typeparam name="T">The type of the result value.</typeparam>
+  /// <returns>The result of the tool call as an instance of <see cref="ToolCallResult{T}"/>.</returns>
+  /// <exception cref="ArgumentException">Thrown when a parameter name is not found.</exception>
+  /// <exception cref="ArgumentException">Thrown when an argument is missing.</exception>
+  public async Task<ToolCallResult<T>> InvokeAsync<T>()
+  {
+    try
+    {
+      T? result = default;
+
+      var arguments = GetArguments();
+      var isAwaitable = Tool.Function.Method.ReturnType.GetMethod(nameof(Task.GetAwaiter)) is not null;
+
+      if (isAwaitable)
+      {
+        var task = (Task)Tool.Function.Method.Invoke(Tool.Function.Instance, arguments);
+        
+        await task;
+        
+        const string resultPropertyName = "Result";
+        var resultProperty = task.GetType().GetProperty(resultPropertyName);
+        result = resultProperty is not null ? (T)resultProperty.GetValue(task) : default;
+      }
+      else
+      {
+        result = (T)Tool.Function.Method.Invoke(Tool.Function.Instance, arguments);
+      }
+
+      return ToolCallResult<T>.Success(result);
+    }
+    catch (Exception e)
+    {
+      return ToolCallResult<T>.Failure(e);
+    }
+  }
+
+  private object?[] GetArguments()
+  {
+    var parameters = Tool.Function.Method.GetParameters();
+    var arguments = new object?[parameters.Length];
+
+    for (var i = 0; i < parameters.Length; i++)
+    {
+      var parameter = parameters[i];
+      var attribute = parameter.GetCustomAttribute<FunctionParameterAttribute>();
+      var parameterName = attribute is not null 
+        ? string.IsNullOrWhiteSpace(attribute.Name) 
+          ? parameter.Name 
+          : attribute.Name
+        : parameter.Name;
+
+      if (parameterName == null)
+      {
+        throw new ArgumentException($"Failed to find a valid parameter name for {Tool.Function.Method.DeclaringType}.{Tool.Function.Method.Name}()");
+      }
+
+      if (ToolUse.Input.TryGetValue(parameterName, out var value))
+      {
+        arguments[i] = value is string s && parameter.ParameterType.IsEnum
+          ? Enum.Parse(parameter.ParameterType, s, true)
+          : value is JsonElement element
+            ? JsonSerializer.Deserialize(element.GetRawText(), parameter.ParameterType, JsonSerializationOptions.DefaultOptions)
+            : value;
+      }
+      else
+      {
+        arguments[i] = parameter.HasDefaultValue
+          ? parameter.DefaultValue
+          : throw new ArgumentException($"Missing argument for parameter '{parameter.Name}'");
+      }
+    }
+
+    return arguments;
+  }
 }

src/AnthropicClient/Models/ToolCallResult.cs

@@ -0,0 +1,56 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a tool call result.
+/// </summary>
+public class ToolCallResult<T>
+{
+  /// <summary>
+  /// The value of the tool call result.
+  /// </summary>
+  public T? Value { get; }
+
+  /// <summary>
+  /// The error of the tool call result.
+  /// </summary>
+  public Exception Error { get; }
+
+  /// <summary>
+  /// Indicates whether the tool call was successful.
+  /// </summary>
+  public bool IsSuccess { get; }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="ToolCallResult{T}"/> class.
+  /// </summary>
+  /// <param name="value">The value of the tool call result.</param>
+  /// <param name="error">The error of the tool call result.</param>
+  /// <param name="isSuccess">Indicates whether the tool call was successful.</param>
+  /// <returns>A new instance of the <see cref="ToolCallResult{T}"/> class.</returns>
+  protected ToolCallResult(T? value, Exception error, bool isSuccess)
+  {
+    Value = value;
+    Error = error;
+    IsSuccess = isSuccess;
+  }
+
+  /// <summary>
+  /// Creates a successful tool call result.
+  /// </summary>
+  /// <param name="value">The value of the tool call result.</param>
+  /// <returns>A new instance of the <see cref="ToolCallResult{T}"/> class.</returns>
+  public static ToolCallResult<T> Success(T? value)
+  {
+    return new ToolCallResult<T>(value, null!, true);
+  }
+
+  /// <summary>
+  /// Creates a failed ool call result.
+  /// </summary>
+  /// <param name="error">The error of the tool call result.</param>
+  /// <returns>A new instance of the <see cref="ToolCallResult{T}"/> class.</returns>
+  public static ToolCallResult<T> Failure(Exception error)
+  {
+    return new ToolCallResult<T>(default!, error, false);
+  }
+}

tests/AnthropicClient.Tests/Unit/Models/ToolCallTests.cs

@@ -0,0 +1,149 @@
+namespace AnthropicClient.Tests.Unit.Models;
+
+public class ToolCallTests
+{
+  [Fact]
+  public async Task InvokeAsync_WhenCalledToolHasNoParamsIsNotAwaitableAndToolCallIsSuccessful_ItShouldReturnSuccessResult()
+  {
+    var func = () => "Hello, World!";
+    var anthropicFunction = new AnthropicFunction(func.Method, func.Target);
+    var tool = new Tool("tool", "description", anthropicFunction);
+    var toolCall = new ToolCall(tool, new ToolUseContent());
+
+    var result = await toolCall.InvokeAsync();
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().Be("Hello, World!");
+    result.Error.Should().BeNull();
+  }
+
+  [Fact]
+  public async Task InvokeAsync_WhenCalledToolHasNoParamsIsNotAwaitableAndToolCallFails_ItShouldReturnFailureResult()
+  {
+    var func = new Func<string>(() => throw new Exception("Error"));
+    var anthropicFunction = new AnthropicFunction(func.Method, func.Target);
+    var tool = new Tool("tool", "description", anthropicFunction);
+    var toolCall = new ToolCall(tool, new ToolUseContent());
+
+    var result = await toolCall.InvokeAsync();
+
+    result.IsSuccess.Should().BeFalse();
+    result.Value.Should().BeNull();
+    result.Error.Should().NotBeNull();
+  }
+
+  [Fact]
+  public async Task InvokeAsync_WhenCalledToolHasNoParamsIsAwaitableAndToolCallIsSuccessful_ItShouldReturnSuccessResult()
+  {
+    var func = async () => await Task.FromResult("Hello, World!");
+    var anthropicFunction = new AnthropicFunction(func.Method, func.Target);
+    var tool = new Tool("tool", "description", anthropicFunction);
+    var toolCall = new ToolCall(tool, new ToolUseContent());
+
+    var result = await toolCall.InvokeAsync();
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().Be("Hello, World!");
+    result.Error.Should().BeNull();
+  }
+
+  [Fact]
+  public async Task InvokeAsync_WhenCalledToolHasNoParamsIsAwaitableAndToolCallFails_ItShouldReturnFailureResult()
+  {
+    var func = new Func<Task<string>>(() => throw new Exception("Error"));
+    var anthropicFunction = new AnthropicFunction(func.Method, func.Target);
+    var tool = new Tool("tool", "description", anthropicFunction);
+    var toolCall = new ToolCall(tool, new ToolUseContent());
+
+    var result = await toolCall.InvokeAsync();
+
+    result.IsSuccess.Should().BeFalse();
+    result.Value.Should().BeNull();
+    result.Error.Should().NotBeNull();
+  }
+
+  [Fact]
+  public async Task InvokeAsync_WhenCalledToolHasParamsIsNotAwaitableAndToolCallIsSuccessful_ItShouldReturnSuccessResult()
+  {
+    var func = (int i) => i.ToString();
+    var anthropicFunction = new AnthropicFunction(func.Method, func.Target);
+    var tool = new Tool("tool", "description", anthropicFunction);
+
+    var input = new Dictionary<string, object?> { { "i", 42 } };
+    var toolCall = new ToolCall(tool, new ToolUseContent { Input = input });
+
+    var result = await toolCall.InvokeAsync();
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().Be("42");
+    result.Error.Should().BeNull();
+  }
+
+  [Fact]
+  public async Task InvokeAsync_WhenCalledToolHasParamsIsNotAwaitableAndToolCallFails_ItShouldReturnFailureResult()
+  {
+    var func = new Func<int, string>(i => throw new Exception("Error"));
+    var anthropicFunction = new AnthropicFunction(func.Method, func.Target);
+    var tool = new Tool("tool", "description", anthropicFunction);
+
+    var input = new Dictionary<string, object?> { { "i", 42 } };
+    var toolCall = new ToolCall(tool, new ToolUseContent { Input = input });
+
+    var result = await toolCall.InvokeAsync();
+
+    result.IsSuccess.Should().BeFalse();
+    result.Value.Should().BeNull();
+    result.Error.Should().NotBeNull();
+  }
+
+  [Fact]
+  public async Task InvokeAsync_WhenCalledToolHasParamsIsAwaitableAndToolCallIsSuccessful_ItShouldReturnSuccessResult()
+  {
+    var func = async (int i) => await Task.FromResult(i.ToString());
+    var anthropicFunction = new AnthropicFunction(func.Method, func.Target);
+    var tool = new Tool("tool", "description", anthropicFunction);
+
+    var input = new Dictionary<string, object?> { { "i", 42 } };
+    var toolCall = new ToolCall(tool, new ToolUseContent { Input = input });
+
+    var result = await toolCall.InvokeAsync();
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().Be("42");
+    result.Error.Should().BeNull();
+  }
+
+  [Fact]
+  public async Task InvokeAsync_WhenCalledToolHasParamsIsAwaitableAndToolCallFails_ItShouldReturnFailureResult()
+  {
+    var func = new Func<int, Task<string>>(i => throw new Exception("Error"));
+    var anthropicFunction = new AnthropicFunction(func.Method, func.Target);
+    var tool = new Tool("tool", "description", anthropicFunction);
+
+    var input = new Dictionary<string, object?> { { "i", 42 } };
+    var toolCall = new ToolCall(tool, new ToolUseContent { Input = input });
+
+    var result = await toolCall.InvokeAsync();
+
+    result.IsSuccess.Should().BeFalse();
+    result.Value.Should().BeNull();
+    result.Error.Should().NotBeNull();
+  }
+
+  [Fact]
+  public async Task InvokeAsync_WhenCalledAndToolHasCustomParameterName_ItShouldReturnSuccessResult()
+  {
+    var func = ([FunctionParameter("Person's Age", "Age")]int i) => i.ToString();
+    var anthropicFunction = new AnthropicFunction(func.Method, func.Target);
+    var tool = new Tool("tool", "description", anthropicFunction);
+
+    var input = new Dictionary<string, object?> { { "Age", 42 } };
+    var toolCall = new ToolCall(tool, new ToolUseContent { Input = input });
+
+    var result = await toolCall.InvokeAsync();
+
+    result.IsSuccess.Should().BeTrue();
+    result.Value.Should().Be("42");
+    result.Error.Should().BeNull();
+  }
+}