feat: create chat message

src/AnthropicClient/Models/AnthropicError.cs

@@ -0,0 +1,34 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents an error response from the Anthropic API.
+/// </summary>
+public class AnthropicError
+{
+  /// <summary>
+  /// The type of the error.
+  /// </summary>
+  public string Type { get; init; } = "error";
+
+  /// <summary>
+  /// The error object.
+  /// </summary>
+  public Error? Error { get; init; } = null;
+
+  [JsonConstructor]
+  internal AnthropicError()
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="AnthropicError"/> class.
+  /// </summary>
+  /// <param name="error">The error as an <see cref="Error"/> object.</param>
+  /// <returns>A new instance of the <see cref="AnthropicError"/> class.</returns>
+  public AnthropicError(Error error)
+  {
+    Error = error;
+  }
+}

src/AnthropicClient/Models/AnthropicModels.cs

@@ -0,0 +1,29 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Provides constants for the Anthropic models.
+/// </summary>
+public static class AnthropicModels
+{
+  /// <summary>
+  /// The Claude-3 Opus model.
+  /// </summary>
+  public const string Claude3Opus = "claude-3-opus-20240229";
+
+  /// <summary>
+  /// The Claude-3 Sonnet model.
+  /// </summary>
+  public const string Claude3Sonnet = "claude-3-sonnet-20240229";
+
+  /// <summary>
+  /// The Claude-3.5 Sonnet model.
+  /// </summary>
+  public const string Claude35Sonnet = "claude-3-5-sonnet-20240620";
+
+  /// <summary>
+  /// The Claude-3 Haiku model.
+  /// </summary>
+  public const string Claude3Haiku = "claude-3-haiku-20240307";
+
+  internal static bool IsValidModel(string modelId) => modelId is Claude3Opus or Claude3Sonnet or Claude35Sonnet or Claude3Haiku;
+}

src/AnthropicClient/Models/AnthropicResult.cs

@@ -0,0 +1,66 @@
+using AnthropicClient.Models;
+
+/// <summary>
+/// Represents the result of an Anthropic API operation.
+/// </summary>
+/// <typeparam name="T">The type of the result value.</typeparam>
+public class AnthropicResult<T>
+{
+  /// <summary>
+  /// The value of the result.
+  /// </summary>
+  public T Value { get; }
+
+  /// <summary>
+  /// The error of the result.
+  /// </summary>
+  public AnthropicError Error { get; }
+
+  /// <summary>
+  /// Indicates whether the operation was successful.
+  /// </summary>
+  public bool IsSuccess { get; }
+
+  /// <summary>
+  /// The request ID of the operation.
+  /// </summary>
+  public string RequestId { get; }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="AnthropicResult{T}"/> class.
+  /// </summary>
+  /// <param name="value">The value of the result.</param>
+  /// <param name="error">The error of the result.</param>
+  /// <param name="isSuccess">Indicates whether the operation was successful.</param>
+  /// <param name="requestId">The request ID of the operation.</param>
+  /// <returns>A new instance of the <see cref="AnthropicResult{T}"/> class.</returns>
+  protected AnthropicResult(T value, AnthropicError error, bool isSuccess, string requestId)
+  {
+    Value = value;
+    Error = error;
+    IsSuccess = isSuccess;
+    RequestId = requestId;
+  }
+
+  /// <summary>
+  /// Creates a successful result.
+  /// </summary>
+  /// <param name="value">The value of the result.</param>
+  /// <param name="requestId">The request ID of the operation.</param>
+  /// <returns>A new instance of the <see cref="AnthropicResult{T}"/> class.</returns>
+  public static AnthropicResult<T> Success(T value, string requestId)
+  {
+    return new AnthropicResult<T>(value, null!, true, requestId);
+  }
+
+  /// <summary>
+  /// Creates a failed result.
+  /// </summary>
+  /// <param name="error">The error of the result.</param>
+  /// <param name="requestId">The request ID of the operation.</param>
+  /// <returns>A new instance of the <see cref="AnthropicResult{T}"/> class.</returns>
+  public static AnthropicResult<T> Failure(AnthropicError error, string requestId)
+  {
+    return new AnthropicResult<T>(default!, error, false, requestId);
+  }
+}

src/AnthropicClient/Models/AnyToolChoice.cs

@@ -0,0 +1,13 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents the any tool choice mode.
+/// </summary>
+public class AnyToolChoice : ToolChoice
+{
+  /// <summary>
+  /// Initializes a new instance of the <see cref="AnyToolChoice"/> class.
+  /// </summary>
+  /// <returns>A new instance of the <see cref="AnyToolChoice"/> class.</returns>
+  public AnyToolChoice() : base(ToolChoiceType.Any) { }
+}

src/AnthropicClient/Models/ApiError.cs

@@ -0,0 +1,24 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents an api_error response from the Anthropic API.
+/// </summary>
+public class ApiError : Error
+{
+  [JsonConstructor]
+  internal ApiError() : base(ErrorType.ApiError)
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="ApiError"/> class.
+  /// </summary>
+  /// <param name="message">The error message.</param>
+  /// <returns>A new instance of the <see cref="ApiError"/> class.</returns>
+  public ApiError(string message) : base(ErrorType.ApiError)
+  {
+    Message = message;
+  }
+}

src/AnthropicClient/Models/AuthenticationError.cs

@@ -0,0 +1,24 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents an authentication_error response from the Anthropic API.
+/// </summary>
+public class AuthenticationError : Error
+{
+  [JsonConstructor]
+  internal AuthenticationError() : base(ErrorType.AuthenticationError)
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="AuthenticationError"/> class.
+  /// </summary>
+  /// <param name="message">The error message.</param>
+  /// <returns>A new instance of the <see cref="AuthenticationError"/> class.</returns>
+  public AuthenticationError(string message) : base(ErrorType.AuthenticationError)
+  {
+    Message = message;
+  }
+}

src/AnthropicClient/Models/AutoToolChoice.cs

@@ -0,0 +1,13 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents the auto tool choice mode.
+/// </summary>
+public class AutoToolChoice : ToolChoice
+{
+  /// <summary>
+  /// Initializes a new instance of the <see cref="AutoToolChoice"/> class.
+  /// </summary>
+  /// <returns>A new instance of the <see cref="AutoToolChoice"/> class.</returns>
+  public AutoToolChoice() : base(ToolChoiceType.Auto) { }
+}

src/AnthropicClient/Models/ChatMessage.cs

@@ -0,0 +1,48 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a chat message.
+/// </summary>
+public class ChatMessage
+{
+  /// <summary>
+  /// Gets the role of the message.
+  /// </summary>
+  public string Role { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Gets the contents of the message.
+  /// </summary>
+  public List<Content> Content { get; init; } = [];
+
+  [JsonConstructor]
+  internal ChatMessage()
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="ChatMessage"/> class.
+  /// </summary>
+  /// <param name="role">The role of the message.</param>
+  /// <param name="content">The contents of the message.</param>
+  /// <exception cref="ArgumentException">Thrown when the role is invalid.</exception>
+  /// <exception cref="ArgumentNullException">Thrown when the role or content is null.</exception>
+  /// <returns>A new instance of the <see cref="ChatMessage"/> class.</returns>
+  public ChatMessage(string role, List<Content> content)
+  {
+    ArgumentValidator.ThrowIfNull(role, nameof(role));
+    ArgumentValidator.ThrowIfNull(content, nameof(content));
+
+    if (MessageRole.IsValidRole(role) is false)
+    {
+      throw new ArgumentException($"Invalid role: {role}");
+    }
+
+    Role = role;
+    Content = content;
+  }
+}

src/AnthropicClient/Models/ChatMessageRequest.cs

@@ -0,0 +1,139 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a chat message request.
+/// </summary>
+public class ChatMessageRequest : MessageRequest
+{
+  /// <summary>
+  /// Gets the model ID to use for the request.
+  /// </summary>
+  public string Model { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Gets the system ID to use for the request.
+  /// </summary>
+  public string? System { get; init; } = null;
+
+  /// <summary>
+  /// Gets the messages to send to the model.
+  /// </summary>
+  public List<ChatMessage> Messages { get; init; } = [];
+
+  /// <summary>
+  /// Gets the maximum number of tokens to generate.
+  /// </summary>
+  [JsonPropertyName("max_tokens")]
+  public int MaxTokens { get; init; } = 1024;
+
+  /// <summary>
+  /// Gets the metadata to include with the request.
+  /// </summary>
+  public Dictionary<string, object>? Metadata { get; init; } = null;
+
+  /// <summary>
+  /// Gets the prompt stop sequences.
+  /// </summary>
+  [JsonPropertyName("stop_sequences")]
+  public List<string> StopSequences { get; init; } = [];
+
+  /// <summary>
+  /// Gets the temperature to use for the request.
+  /// </summary>
+  public decimal Temperature { get; init; } = 0.0m;
+
+  /// <summary>
+  /// Gets the top-K value to use for the request.
+  /// </summary>
+  public int? TopK { get; init; } = null;
+
+  /// <summary>
+  /// Gets the top-P value to use for the request.
+  /// </summary>
+  public decimal? TopP { get; init; } = null;
+
+  /// <summary>
+  /// Gets the tool choice mode to use for the request.
+  /// </summary>
+  [JsonPropertyName("tool_choice")]
+  public ToolChoice? ToolChoice { get; init; } = null;
+
+  /// <summary>
+  /// Gets the tools to use for the request.
+  /// </summary>
+  public List<Tool>? Tools { get; init; } = null;
+
+  [JsonConstructor]
+  internal ChatMessageRequest() : base(false) { }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="ChatMessageRequest"/> class.
+  /// </summary>
+  /// <param name="model">The model ID to use for the request.</param>
+  /// <param name="messages">The messages to send to the model.</param>
+  /// <param name="maxTokens">The maximum number of tokens to generate.</param>
+  /// <param name="system">The system ID to use for the request.</param>
+  /// <param name="metadata">The metadata to include with the request.</param>
+  /// <param name="temperature">The temperature to use for the request.</param>
+  /// <param name="topK">The top-K value to use for the request.</param>
+  /// <param name="topP">The top-P value to use for the request.</param>
+  /// <param name="toolChoice">The tool choice mode to use for the request.</param>
+  /// <param name="tools">The tools to use for the request.</param>
+  /// <exception cref="ArgumentException">Thrown when the model ID is invalid.</exception>
+  /// <exception cref="ArgumentNullException">Thrown when the model or messages is null.</exception>
+  /// <exception cref="ArgumentException">Thrown when the messages contain no messages.</exception>
+  /// <exception cref="ArgumentException">Thrown when the max tokens is less than one.</exception>
+  /// <exception cref="ArgumentException">Thrown when the temperature is less than zero or greater than one.</exception>
+  /// <returns>A new instance of the <see cref="ChatMessageRequest"/> class.</returns>
+  public ChatMessageRequest(
+    string model,
+    List<ChatMessage> messages,
+    int maxTokens = 1024,
+    string? system = null,
+    Dictionary<string, object>? metadata = null,
+    decimal temperature = 0.0m,
+    int? topK = null,
+    decimal? topP = null,
+    ToolChoice? toolChoice = null,
+    List<Tool>? tools = null
+  ) : base(false)
+  {
+    ArgumentValidator.ThrowIfNull(model, nameof(model));
+    ArgumentValidator.ThrowIfNull(messages, nameof(messages));
+
+    if (AnthropicModels.IsValidModel(model) is false)
+    {
+      throw new ArgumentException($"Invalid model ID: {model}");
+    }
+
+    if (messages.Count < 1)
+    {
+      throw new ArgumentException("Messages must contain at least one message");
+    }
+
+    if (maxTokens < 1)
+    {
+      throw new ArgumentException($"Invalid max tokens: {maxTokens}");
+    }
+
+    if (temperature < 0.0m || temperature > 1.0m)
+    {
+      throw new ArgumentException($"Invalid temperature: {temperature}");
+    }
+
+    Model = model;
+    Messages = messages;
+    MaxTokens = maxTokens;
+    System = system;
+    Metadata = metadata;
+    Temperature = temperature;
+    TopK = topK;
+    TopP = topP;
+    ToolChoice = toolChoice;
+    Tools = tools;
+  }
+}

src/AnthropicClient/Models/ChatResponse.cs

@@ -0,0 +1,51 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a chat response.
+/// </summary>
+public class ChatResponse
+{
+  /// <summary>
+  /// Gets the ID of the chat response.
+  /// </summary>
+  public string Id { get; set; } = string.Empty;
+
+  /// <summary>
+  /// Gets the model used for the chat response.
+  /// </summary>
+  public string Model { get; set; } = string.Empty;
+
+  /// <summary>
+  /// Gets the role of the chat response.
+  /// </summary>
+  public string Role { get; set; } = string.Empty;
+
+  /// <summary>
+  /// Gets the stop reason of the chat response.
+  /// </summary>
+  [JsonPropertyName("stop_reason")]
+  public string StopReason { get; set; } = string.Empty;
+
+  /// <summary>
+  /// Gets the stop sequence of the chat response.
+  /// </summary>
+  [JsonPropertyName("stop_sequence")]
+  public string StopSequence { get; set; } = string.Empty;
+
+  /// <summary>
+  /// Gets the type of the chat response.
+  /// </summary>
+  public string Type { get; set; } = string.Empty;
+
+  /// <summary>
+  /// Gets the usage of the chat response.
+  /// </summary>
+  public ChatUsage Usage { get; set; } = new();
+
+  /// <summary>
+  /// Gets the contents of the chat response.
+  /// </summary>
+  public List<Content> Content { get; set; } = [];
+}

src/AnthropicClient/Models/ChatUsage.cs

@@ -0,0 +1,21 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents the usage of a chat response.
+/// </summary>
+public class ChatUsage
+{
+  /// <summary>
+  /// Gets the number of input tokens used.
+  /// </summary>
+  [JsonPropertyName("input_tokens")]
+  public int InputTokens { get; set; }
+
+  /// <summary>
+  /// Gets the number of output tokens used.
+  /// </summary>
+  [JsonPropertyName("output_tokens")]
+  public int OutputTokens { get; set; }
+}

src/AnthropicClient/Models/Client.cs

@@ -0,0 +1,83 @@
+using System.Net.Http.Headers;
+using System.Text;
+using System.Text.Json;
+
+using AnthropicClient.Json;
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a client for interacting with the Anthropic API.
+/// </summary>
+public interface IClient
+{
+  /// <summary>
+  /// Creates a chat message asynchronously.
+  /// </summary>
+  /// <param name="request">The chat message request to create.</param>
+  /// <returns>A task that represents the asynchronous operation. The task result contains the chat response as an <see cref="AnthropicResult{T}"/>.</returns>
+  Task<AnthropicResult<ChatResponse>> CreateChatMessageAsync(ChatMessageRequest request);
+}
+
+/// <inheritdoc cref="IClient"/>
+public class Client : IClient
+{
+  private const string BaseUrl = "https://api.anthropic.com/v1/";
+  private const string ApiKeyHeader = "x-api-key";
+  private const string MessagesEndpoint = "messages";
+  private const string JsonContentType = "application/json";
+  private const string RequestIdHeader = "request-id";
+  private readonly Dictionary<string, string> _defaultHeaders = new()
+  {
+    { "anthropic-version", "2023-06-01" },
+  };
+  private readonly HttpClient _httpClient;
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="Client"/> class.
+  /// </summary>
+  /// <param name="apiKey">The API key to use for the client.</param>
+  /// <param name="httpClient">The HTTP client to use for the client.</param>
+  /// <exception cref="ArgumentNullException">Thrown when the API key or HTTP client is null.</exception>
+  /// <returns>A new instance of the <see cref="Client"/> class.</returns>
+  public Client(string apiKey, HttpClient httpClient)
+  {
+    ArgumentValidator.ThrowIfNull(apiKey, nameof(apiKey));
+    ArgumentValidator.ThrowIfNull(httpClient, nameof(httpClient));
+
+    _httpClient = httpClient;
+    _httpClient.BaseAddress = new Uri(BaseUrl);
+    _httpClient.DefaultRequestHeaders.Add(ApiKeyHeader, apiKey);
+    _httpClient.DefaultRequestHeaders
+      .Accept
+      .Add(new MediaTypeWithQualityHeaderValue(JsonContentType));
+
+    foreach (var pair in _defaultHeaders)
+    {
+      _httpClient.DefaultRequestHeaders.Add(pair.Key, pair.Value);
+    }
+  }
+
+  /// <inheritdoc />
+  public async Task<AnthropicResult<ChatResponse>> CreateChatMessageAsync(ChatMessageRequest request)
+  {
+    var requestContent = new StringContent(Serialize(request), Encoding.UTF8, JsonContentType);
+    var response = await _httpClient.PostAsync(MessagesEndpoint, requestContent);
+    var requestId = GetRequestId(response);
+    var responseContent = await response.Content.ReadAsStringAsync();
+
+    if (response.IsSuccessStatusCode is false)
+    {
+      var error = Deserialize<AnthropicError>(responseContent) ?? new AnthropicError();
+      return AnthropicResult<ChatResponse>.Failure(error, requestId);
+    }
+
+    var chatResponse = Deserialize<ChatResponse>(responseContent) ?? new ChatResponse();
+    return AnthropicResult<ChatResponse>.Success(chatResponse, requestId);
+  }
+
+  private string Serialize<T>(T obj) => JsonSerializer.Serialize(obj, JsonSerializationOptions.DefaultOptions);
+  private T? Deserialize<T>(string json) => JsonSerializer.Deserialize<T>(json, JsonSerializationOptions.DefaultOptions);
+  private string GetRequestId(HttpResponseMessage response) => response.Headers.GetValues(RequestIdHeader).FirstOrDefault() ?? string.Empty;
+}

src/AnthropicClient/Models/Content.cs

@@ -0,0 +1,29 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents part of the content of a chat message.
+/// </summary>
+public abstract class Content
+{
+  /// <summary>
+  /// Gets the type of the content.
+  /// </summary>
+  public string Type { get; init; } = string.Empty;
+
+  [JsonConstructor]
+  internal Content()
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="Content"/> class.
+  /// </summary>
+  /// <param name="type">The type of the content.</param>
+  /// <returns>A new instance of the <see cref="Content"/> class.</returns>
+  protected Content(string type)
+  {
+    Type = type;
+  }
+}

src/AnthropicClient/Models/ContentType.cs

@@ -0,0 +1,27 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents the content type.
+/// </summary>
+public static class ContentType
+{
+  /// <summary>
+  /// Represents the text content type.
+  /// </summary>
+  public const string Text = "text";
+
+  /// <summary>
+  /// Represents the image content type.
+  /// </summary>
+  public const string Image = "image";
+
+  /// <summary>
+  /// Represents the tool use content type.
+  /// </summary>
+  public const string ToolUse = "tool_use";
+
+  /// <summary>
+  /// Represents the tool result content type.
+  /// </summary>
+  public const string ToolResult = "tool_result";
+}

src/AnthropicClient/Models/Error.cs

@@ -0,0 +1,27 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents an error.
+/// </summary>
+public abstract class Error
+{
+  /// <summary>
+  /// Gets the type of the error.
+  /// </summary>
+  public string Type { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Gets the message of the error.
+  /// </summary>
+  public string Message { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="Error"/> class.
+  /// </summary>
+  /// <param name="type">The type of the error.</param>
+  /// <returns>A new instance of the <see cref="Error"/> class.</returns>
+  protected Error(string type)
+  {
+    Type = type;
+  }
+}

src/AnthropicClient/Models/ErrorType.cs

@@ -0,0 +1,42 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents the error type.
+/// </summary>
+public class ErrorType
+{
+  /// <summary>
+  /// Represents the invalid_request error type.
+  /// </summary>
+  public const string InvalidRequestError = "invalid_request_error";
+
+  /// <summary>
+  /// Represents the authentication_error type.
+  /// </summary>
+  public const string AuthenticationError = "authentication_error";
+
+  /// <summary>
+  /// Represents the permission_error type.
+  /// </summary>
+  public const string PermissionError = "permission_error";
+
+  /// <summary>
+  /// Represents the not_found_error type.
+  /// </summary>
+  public const string NotFoundError = "not_found_error";
+
+  /// <summary>
+  /// Represents the rate_limit_error type.
+  /// </summary>
+  public const string RateLimitError = "rate_limit_error";
+
+  /// <summary>
+  /// Represents the api_error type.
+  /// </summary>
+  public const string ApiError = "api_error";
+
+  /// <summary>
+  /// Represents the overloaded_error type.
+  /// </summary>
+  public const string OverloadedError = "overloaded_error";
+}

src/AnthropicClient/Models/ImageContent.cs

@@ -0,0 +1,36 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents image content that is part of a chat message.
+/// </summary>
+public class ImageContent : Content
+{
+  /// <summary>
+  /// Gets the source of the image.
+  /// </summary>
+  public ImageSource Source { get; init; } = new();
+
+  [JsonConstructor]
+  internal ImageContent()
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="ImageContent"/> class.
+  /// </summary>
+  /// <param name="mediaType">The media type of the image.</param>
+  /// <param name="data">The data of the image.</param>
+  /// <exception cref="ArgumentNullException">Thrown when the media type or data is null.</exception>
+  /// <returns>A new instance of the <see cref="ImageContent"/> class.</returns>
+  public ImageContent(string mediaType, string data) : base(ContentType.Image)
+  {
+    ArgumentValidator.ThrowIfNull(mediaType, nameof(mediaType));
+    ArgumentValidator.ThrowIfNull(data, nameof(data));
+
+    Source = new(mediaType, data);
+  }
+}

src/AnthropicClient/Models/ImageSource.cs

@@ -0,0 +1,50 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents an image source.
+/// </summary>
+public class ImageSource
+{
+  /// <summary>
+  /// Gets the media type of the image.
+  /// </summary>
+  [JsonPropertyName("media_type")]
+  public string MediaType { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Gets the data of the image.
+  /// </summary>
+  public string Data { get; init; } = string.Empty;
+
+  [JsonConstructor]
+  internal ImageSource()
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="ImageSource"/> class.
+  /// </summary>
+  /// <param name="mediaType">The media type of the image.</param>
+  /// <param name="data">The data of the image.</param>
+  /// <exception cref="ArgumentException">Thrown when the media type is invalid.</exception>
+  /// <exception cref="ArgumentNullException">Thrown when the media type or data is null.</exception>
+  /// <returns>A new instance of the <see cref="ImageSource"/> class.</returns>
+  public ImageSource(string mediaType, string data)
+  {
+    ArgumentValidator.ThrowIfNull(mediaType, nameof(mediaType));
+
+    if (ImageType.IsValidImageType(mediaType) is false)
+    {
+      throw new ArgumentException($"Invalid media type: {mediaType}");
+    }
+
+    ArgumentValidator.ThrowIfNull(data, nameof(data));
+
+    MediaType = mediaType;
+    Data = data;
+  }
+}

src/AnthropicClient/Models/ImageType.cs

@@ -0,0 +1,29 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents the image type.
+/// </summary>
+public static class ImageType
+{
+  /// <summary>
+  /// Represents the JPEG image type.
+  /// </summary>
+  public const string Jpg = "image/jpeg";
+
+  /// <summary>
+  /// Represents the PNG image type.
+  /// </summary>
+  public const string Png = "image/png";
+
+  /// <summary>
+  /// Represents the GIF image type.
+  /// </summary>
+  public const string Gif = "image/gif";
+
+  /// <summary>
+  /// Represents the WebP image type.
+  /// </summary>
+  public const string Webp = "image/webp";
+  
+  internal static bool IsValidImageType(string imageType) => imageType is Jpg or Png or Gif or Webp;
+}

src/AnthropicClient/Models/InputProperty.cs

@@ -0,0 +1,42 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents an input property.
+/// </summary>
+public class InputProperty
+{
+  /// <summary>
+  /// Gets the type of the input property.
+  /// </summary>
+  public string Type { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Gets the description of the input property.
+  /// </summary>
+  public string Description { get; init; } = string.Empty;
+
+  [JsonConstructor]
+  internal InputProperty()
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="InputProperty"/> class.
+  /// </summary>
+  /// <param name="type">The type of the input property.</param>
+  /// <param name="description">The description of the input property.</param>
+  /// <exception cref="ArgumentNullException">Thrown when the type or description is null.</exception>
+  /// <returns>A new instance of the <see cref="InputProperty"/> class.</returns>
+  public InputProperty(string type, string description)
+  {
+    ArgumentValidator.ThrowIfNull(type, nameof(type));
+    ArgumentValidator.ThrowIfNull(description, nameof(description));
+
+    Type = type;
+    Description = description;
+  }
+}

src/AnthropicClient/Models/InputSchema.cs

@@ -0,0 +1,53 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents an input schema.
+/// </summary>
+public class InputSchema
+{
+  /// <summary>
+  /// Gets the type of the input schema.
+  /// </summary>
+  public string Type { get; init; } = "object";
+
+  /// <summary>
+  /// Gets the properties of the input schema.
+  /// </summary>
+  public Dictionary<string, InputProperty> Properties { get; init; } = [];
+
+  /// <summary>
+  /// Gets the required properties of the input schema.
+  /// </summary>
+  public List<string> Required { get; init; } = [];
+
+  [JsonConstructor]
+  internal InputSchema()
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="InputSchema"/> class.
+  /// </summary>
+  /// <param name="properties">The properties of the input schema.</param>
+  /// <param name="required">The required properties of the input schema.</param>
+  /// <exception cref="ArgumentNullException">Thrown when the properties or required is null.</exception>
+  /// <exception cref="ArgumentException">Thrown when the required properties are not present in the properties dictionary.</exception>
+  /// <returns>A new instance of the <see cref="InputSchema"/> class.</returns>
+  public InputSchema(Dictionary<string, InputProperty> properties, List<string> required)
+  {
+    ArgumentValidator.ThrowIfNull(properties, nameof(properties));
+    ArgumentValidator.ThrowIfNull(required, nameof(required));
+
+    if (required.Any(r => properties.ContainsKey(r) is false))
+    {
+      throw new ArgumentException("Required properties must be present in the properties dictionary.");
+    }
+
+    Properties = properties;
+    Required = required;
+  }
+}

src/AnthropicClient/Models/InvalidRequestError.cs

@@ -0,0 +1,24 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents an invalid_request error.
+/// </summary>
+public class InvalidRequestError : Error
+{
+  [JsonConstructor]
+  internal InvalidRequestError() : base(ErrorType.InvalidRequestError)
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="InvalidRequestError"/> class.
+  /// </summary>
+  /// <param name="message">The message of the error.</param>
+  /// <returns>A new instance of the <see cref="InvalidRequestError"/> class.</returns>
+  public InvalidRequestError(string message) : base(ErrorType.InvalidRequestError)
+  {
+    Message = message;
+  }
+}

src/AnthropicClient/Models/IsExternalInit.cs

@@ -0,0 +1,7 @@
+using System.ComponentModel;
+
+namespace System.Runtime.CompilerServices
+{
+  [EditorBrowsable(EditorBrowsableState.Never)]
+  class IsExternalInit { }
+}

src/AnthropicClient/Models/MessageRequest.cs

@@ -0,0 +1,22 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a message request.
+/// </summary>
+public abstract class MessageRequest
+{
+  /// <summary>
+  /// Gets a value indicating whether the message should be streamed.
+  /// </summary>
+  public bool Stream { get; init; }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="MessageRequest"/> class.
+  /// </summary>
+  /// <param name="stream">A value indicating whether the message should be streamed.</param>
+  /// <returns>A new instance of the <see cref="MessageRequest"/> class.</returns>
+  public MessageRequest(bool stream = false)
+  {
+    Stream = stream;
+  }
+}

src/AnthropicClient/Models/MessageRole.cs

@@ -0,0 +1,19 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents the message role.
+/// </summary>
+public static class MessageRole
+{
+  /// <summary>
+  /// Represents the user role.
+  /// </summary>
+  public const string User = "user";
+
+  /// <summary>
+  /// Represents the assistant role.
+  /// </summary>
+  public const string Assistant = "assistant";
+  
+  internal static bool IsValidRole(string role) => role is User or Assistant;
+}

src/AnthropicClient/Models/NotFoundError.cs

@@ -0,0 +1,24 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a not_found error.
+/// </summary>
+public class NotFoundError : Error
+{
+  [JsonConstructor]
+  internal NotFoundError() : base(ErrorType.NotFoundError)
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="NotFoundError"/> class.
+  /// </summary>
+  /// <param name="message">The message of the error.</param>
+  /// <returns>A new instance of the <see cref="NotFoundError"/> class.</returns>
+  public NotFoundError(string message) : base(ErrorType.NotFoundError)
+  {
+    Message = message;
+  }
+}

src/AnthropicClient/Models/OverloadedError.cs

@@ -0,0 +1,24 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents an overloaded error.
+/// </summary>
+public class OverloadedError : Error
+{
+  [JsonConstructor]
+  internal OverloadedError() : base(ErrorType.OverloadedError)
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="OverloadedError"/> class.
+  /// </summary>
+  /// <param name="message">The message of the error.</param>
+  /// <returns>A new instance of the <see cref="OverloadedError"/> class.</returns>
+  public OverloadedError(string message) : base(ErrorType.OverloadedError)
+  {
+    Message = message;
+  }
+}

src/AnthropicClient/Models/PermissionError.cs

@@ -0,0 +1,24 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a permission error.
+/// </summary>
+public class PermissionError : Error
+{
+  [JsonConstructor]
+  internal PermissionError() : base(ErrorType.PermissionError)
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="PermissionError"/> class.
+  /// </summary>
+  /// <param name="message">The message of the error.</param>
+  /// <returns>A new instance of the <see cref="PermissionError"/> class.</returns>
+  public PermissionError(string message) : base(ErrorType.PermissionError)
+  {
+    Message = message;
+  }
+}

src/AnthropicClient/Models/RateLimitError.cs

@@ -0,0 +1,24 @@
+using System.Text.Json.Serialization;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a rate_limit error.
+/// </summary>
+public class RateLimitError : Error
+{
+  [JsonConstructor]
+  internal RateLimitError() : base(ErrorType.RateLimitError)
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="RateLimitError"/> class.
+  /// </summary>
+  /// <param name="message">The message of the error.</param>
+  /// <returns>A new instance of the <see cref="RateLimitError"/> class.</returns>
+  public RateLimitError(string message) : base(ErrorType.RateLimitError)
+  {
+    Message = message;
+  }
+}

src/AnthropicClient/Models/SpecificToolChoice.cs

@@ -0,0 +1,34 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents the specific tool choice mode.
+/// </summary>
+public class SpecificToolChoice : ToolChoice
+{
+  /// <summary>
+  /// Gets the name of the tool.
+  /// </summary>
+  public string Name { get; init; } = string.Empty;
+
+  [JsonConstructor]
+  internal SpecificToolChoice() : base(ToolChoiceType.Tool)
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="SpecificToolChoice"/> class.
+  /// </summary>
+  /// <param name="name">The name of the tool.</param>
+  /// <exception cref="ArgumentNullException">Thrown when the name is null.</exception>
+  /// <returns>A new instance of the <see cref="SpecificToolChoice"/> class.</returns>
+  public SpecificToolChoice(string name) : base(ToolChoiceType.Tool)
+  {
+    ArgumentValidator.ThrowIfNull(name, nameof(name));
+
+    Name = name;
+  }
+}

src/AnthropicClient/Models/StopReasonType.cs

@@ -0,0 +1,27 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents the stop reason type.
+/// </summary>
+public static class StopReasonType
+{
+  /// <summary>
+  /// Represents the end_turn stop reason.
+  /// </summary>
+  public const string EndTurn = "end_turn";
+
+  /// <summary>
+  /// Represents the max_tokens stop reason.
+  /// </summary>
+  public const string MaxTokens = "max_tokens";
+
+  /// <summary>
+  /// Represents the stop_sequence stop reason.
+  /// </summary>
+  public const string StopSequence = "stop_sequence";
+
+  /// <summary>
+  /// Represents the tool_use stop reason.
+  /// </summary>
+  public const string ToolUse = "tool_use";
+}

src/AnthropicClient/Models/TextContent.cs

@@ -0,0 +1,34 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents text content that is part of a chat message.
+/// </summary>
+public class TextContent : Content
+{
+  /// <summary>
+  /// Gets the text of the content.
+  /// </summary>
+  public string Text { get; init; } = string.Empty;
+
+  [JsonConstructor]
+  internal TextContent() : base(ContentType.Text)
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="TextContent"/> class.
+  /// </summary>
+  /// <param name="text">The text of the content.</param>
+  /// <exception cref="ArgumentNullException">Thrown when the text is null.</exception>
+  /// <returns>A new instance of the <see cref="TextContent"/> class.</returns>
+  public TextContent(string text) : base(ContentType.Text)
+  {
+    ArgumentValidator.ThrowIfNull(text, nameof(text));
+
+    Text = text;
+  }
+}

src/AnthropicClient/Models/Tool.cs

@@ -0,0 +1,51 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a tool that can be used in the chat.
+/// </summary>
+public class Tool
+{
+  /// <summary>
+  /// Gets the name of the tool.
+  /// </summary>
+  public string Name { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Gets the description of the tool.
+  /// </summary>
+  public string Description { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Gets the input schema of the tool.
+  /// </summary>
+  [JsonPropertyName("input_schema")]
+  public InputSchema InputSchema { get; init; } = new();
+
+  [JsonConstructor]
+  internal Tool()
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="Tool"/> class.
+  /// </summary>
+  /// <param name="name">The name of the tool.</param>
+  /// <param name="description">The description of the tool.</param>
+  /// <param name="inputSchema">The input schema of the tool.</param>
+  /// <exception cref="ArgumentNullException">Thrown when the name, description, or input schema is null.</exception>
+  /// <returns>A new instance of the <see cref="Tool"/> class.</returns>
+  public Tool(string name, string description, InputSchema inputSchema)
+  {
+    ArgumentValidator.ThrowIfNull(name, nameof(name));
+    ArgumentValidator.ThrowIfNull(description, nameof(description));
+    ArgumentValidator.ThrowIfNull(inputSchema, nameof(inputSchema));
+
+    Name = name;
+    Description = description;
+    InputSchema = inputSchema;
+  }
+}

src/AnthropicClient/Models/ToolChoice.cs

@@ -0,0 +1,22 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a tool choice mode.
+/// </summary>
+public abstract class ToolChoice
+{
+  /// <summary>
+  /// Gets the type of the tool choice.
+  /// </summary>
+  public string Type { get; init; } = string.Empty;
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="ToolChoice"/> class.
+  /// </summary>
+  /// <param name="type">The type of the tool choice.</param>
+  /// <returns>A new instance of the <see cref="ToolChoice"/> class.</returns>
+  protected ToolChoice(string type)
+  {
+    Type = type;
+  }
+}

src/AnthropicClient/Models/ToolChoiceType.cs

@@ -0,0 +1,24 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents the tool choice type.
+/// </summary>
+public class ToolChoiceType
+{
+  /// <summary>
+  /// Represents the auto tool choice type.
+  /// </summary>
+  public const string Auto = "auto";
+
+  /// <summary>
+  /// Represents the any tool choice type.
+  /// </summary>
+  public const string Any = "any";
+
+  /// <summary>
+  /// Represents the specific tool choice type.
+  /// </summary>
+  public const string Tool = "tool";
+  
+  internal static bool IsValidType(string type) => type is Auto or Any or Tool;
+}

src/AnthropicClient/Models/ToolResultContent.cs

@@ -0,0 +1,41 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents tool result content that is part of a chat message.
+/// </summary>
+public class ToolResultContent : Content
+{
+  /// <summary>
+  /// Gets the tool use ID of the content.
+  /// </summary>
+  [JsonPropertyName("tool_use_id")]
+  public string ToolUseId { get; set; } = string.Empty;
+
+  /// <summary>
+  /// Gets the content of the tool result.
+  /// </summary>
+  public string Content { get; set; } = string.Empty;
+
+  [JsonConstructor]
+  internal ToolResultContent() : base(ContentType.ToolResult) { }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="ToolResultContent"/> class.
+  /// </summary>
+  /// <param name="toolUseId">The tool use ID of the content.</param>
+  /// <param name="content">The content of the tool result.</param>
+  /// <exception cref="ArgumentNullException">Thrown when the tool use ID or content is null.</exception>
+  /// <returns>A new instance of the <see cref="ToolResultContent"/> class.</returns>
+  public ToolResultContent(string toolUseId, string content) : base(ContentType.ToolResult)
+  {
+    ArgumentValidator.ThrowIfNull(toolUseId, nameof(toolUseId));
+    ArgumentValidator.ThrowIfNull(content, nameof(content));
+
+    ToolUseId = toolUseId;
+    Content = content;
+  }
+}

src/AnthropicClient/Models/ToolUseContent.cs

@@ -0,0 +1,30 @@
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents tool use content that is part of a message.
+/// </summary>
+public class ToolUseContent : Content
+{
+  /// <summary>
+  /// Gets the ID of the tool use.
+  /// </summary>
+  public string Id { get; set; } = string.Empty;
+
+  /// <summary>
+  /// Gets the name of the tool.
+  /// </summary>
+  public string Name { get; set; } = string.Empty;
+
+  /// <summary>
+  /// Gets the input of the tool.
+  /// </summary>
+  public Dictionary<string, object?> Input { get; set; } = [];
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="ToolUseContent"/> class.
+  /// </summary>
+  /// <returns>A new instance of the <see cref="ToolUseContent"/> class.</returns>
+  public ToolUseContent() : base(ContentType.ToolUse)
+  {
+  }
+}