diff --git a/OpenAI_API/APIAuthentication.cs b/OpenAI_API/APIAuthentication.cs
index 4346281..fe916ad 100644
--- a/OpenAI_API/APIAuthentication.cs
+++ b/OpenAI_API/APIAuthentication.cs
@@ -9,7 +9,7 @@ namespace OpenAI_API
 	/// <summary>
 	/// Represents authentication to the OpenAPI API endpoint
 	/// </summary>
-	public class APIAuthentication
+	public class APIAuthentication : IAPIAuthentication
 	{
 		/// <summary>
 		/// The API key, required to access the API endpoint.
diff --git a/OpenAI_API/IAPIAuthentication.cs b/OpenAI_API/IAPIAuthentication.cs
new file mode 100644
index 0000000..855365b
--- /dev/null
+++ b/OpenAI_API/IAPIAuthentication.cs
@@ -0,0 +1,26 @@
+using System.Threading.Tasks;
+
+namespace OpenAI_API
+{
+    /// <summary>
+    /// Represents authentication to the OpenAPI API endpoint
+    /// </summary>
+    public interface IAPIAuthentication
+    {
+        /// <summary>
+        /// The API key, required to access the API endpoint.
+        /// </summary>
+        string ApiKey { get; set; }
+
+        /// <summary>
+        /// The Organization ID to count API requests against.  This can be found at https://beta.openai.com/account/org-settings.
+        /// </summary>
+        string OpenAIOrganization { get; set; }
+
+        /// <summary>
+        /// Tests the api key against the OpenAI API, to ensure it is valid.  This hits the models endpoint so should not be charged for usage.
+        /// </summary>
+        /// <returns><see langword="true"/> if the api key is valid, or <see langword="false"/> if empty or not accepted by the OpenAI API.</returns>
+        Task<bool> ValidateAPIKey();
+    }
+}
\ No newline at end of file
diff --git a/OpenAI_API/IOpenAIAPI.cs b/OpenAI_API/IOpenAIAPI.cs
index 7b2de67..6bf1b9d 100644
--- a/OpenAI_API/IOpenAIAPI.cs
+++ b/OpenAI_API/IOpenAIAPI.cs
@@ -1,3 +1,4 @@
+using OpenAI_API.Chat;
 using OpenAI_API.Completions;
 using OpenAI_API.Embedding;
 using OpenAI_API.Files;
@@ -25,26 +26,31 @@ public interface IOpenAIAPI
         /// <summary>
         /// The API authentication information to use for API calls
         /// </summary>
-        APIAuthentication Auth { get; set; }
+        IAPIAuthentication Auth { get; set; }
 
         /// <summary>
         /// Text generation is the core function of the API. You give the API a prompt, and it generates a completion. The way you “program” the API to do a task is by simply describing the task in plain english or providing a few written examples. This simple approach works for a wide range of use cases, including summarization, translation, grammar correction, question answering, chatbots, composing emails, and much more (see the prompt library for inspiration).
         /// </summary>
-        CompletionEndpoint Completions { get; }
+        ICompletionEndpoint Completions { get; }
 
         /// <summary>
         /// The API lets you transform text into a vector (list) of floating point numbers. The distance between two vectors measures their relatedness. Small distances suggest high relatedness and large distances suggest low relatedness.
         /// </summary>
-        EmbeddingEndpoint Embeddings { get; }
+        IEmbeddingEndpoint Embeddings { get; }
+        
+        /// <summary>
+        /// Text generation in the form of chat messages. This interacts with the ChatGPT API.
+        /// </summary>
+        IChatEndpoint Chat { get; }
 
         /// <summary>
         /// The API endpoint for querying available Engines/models
         /// </summary>
-        ModelsEndpoint Models { get; }
+        IModelsEndpoint Models { get; }
 
         /// <summary>
         /// The API lets you do operations with files. You can upload, delete or retrieve files. Files can be used for fine-tuning, search, etc.
         /// </summary>
-        FilesEndpoint Files { get; }
+        IFilesEndpoint Files { get; }
     }
 }
\ No newline at end of file
diff --git a/OpenAI_API/OpenAIAPI.cs b/OpenAI_API/OpenAIAPI.cs
index f415410..6159b4e 100644
--- a/OpenAI_API/OpenAIAPI.cs
+++ b/OpenAI_API/OpenAIAPI.cs
@@ -29,7 +29,7 @@ public class OpenAIAPI : IOpenAIAPI
 		/// <summary>
 		/// The API authentication information to use for API calls
 		/// </summary>
-		public APIAuthentication Auth { get; set; }
+		public IAPIAuthentication Auth { get; set; }
 
 		/// <summary>
 		/// Creates a new entry point to the OpenAPI API, handling auth and allowing access to the various API endpoints
@@ -65,37 +65,37 @@ public static OpenAIAPI ForAzure(string YourResourceName, string deploymentId, A
 		/// <summary>
 		/// Text generation is the core function of the API. You give the API a prompt, and it generates a completion. The way you “program” the API to do a task is by simply describing the task in plain english or providing a few written examples. This simple approach works for a wide range of use cases, including summarization, translation, grammar correction, question answering, chatbots, composing emails, and much more (see the prompt library for inspiration).
 		/// </summary>
-		public CompletionEndpoint Completions { get; }
+		public ICompletionEndpoint Completions { get; }
 
 		/// <summary>
 		/// The API lets you transform text into a vector (list) of floating point numbers. The distance between two vectors measures their relatedness. Small distances suggest high relatedness and large distances suggest low relatedness.
 		/// </summary>
-		public EmbeddingEndpoint Embeddings { get; }
+		public IEmbeddingEndpoint Embeddings { get; }
 
 		/// <summary>
 		/// Text generation in the form of chat messages. This interacts with the ChatGPT API.
 		/// </summary>
-		public ChatEndpoint Chat { get; }
+		public IChatEndpoint Chat { get; }
 
 		/// <summary>
 		/// Classify text against the OpenAI Content Policy.
 		/// </summary>
-		public ModerationEndpoint Moderation { get; }
+		public IModerationEndpoint Moderation { get; }
 
 		/// <summary>
 		/// The API endpoint for querying available Engines/models
 		/// </summary>
-		public ModelsEndpoint Models { get; }
+		public IModelsEndpoint Models { get; }
 
 		/// <summary>
 		/// The API lets you do operations with files. You can upload, delete or retrieve files. Files can be used for fine-tuning, search, etc.
 		/// </summary>
-		public FilesEndpoint Files { get; }
+		public IFilesEndpoint Files { get; }
 
 		/// <summary>
 		/// The API lets you do operations with images. You can Given a prompt and/or an input image, the model will generate a new image.
 		/// </summary>
-		public ImageGenerationEndpoint ImageGenerations { get; }
+		public IImageGenerationEndpoint ImageGenerations { get; }
 
 	}
 }
diff --git a/OpenAI_Tests/AuthTests.cs b/OpenAI_Tests/AuthTests.cs
index e791c81..32da514 100644
--- a/OpenAI_Tests/AuthTests.cs
+++ b/OpenAI_Tests/AuthTests.cs
@@ -67,14 +67,14 @@ public void testHelper()
 			OpenAI_API.APIAuthentication defaultAuth = OpenAI_API.APIAuthentication.Default;
 			OpenAI_API.APIAuthentication manualAuth = new OpenAI_API.APIAuthentication("pk-testAA");
 			OpenAI_API.OpenAIAPI api = new OpenAI_API.OpenAIAPI();
-			OpenAI_API.APIAuthentication shouldBeDefaultAuth = api.Auth;
+			OpenAI_API.IAPIAuthentication shouldBeDefaultAuth = api.Auth;
 			Assert.IsNotNull(shouldBeDefaultAuth);
 			Assert.IsNotNull(shouldBeDefaultAuth.ApiKey);
 			Assert.AreEqual(defaultAuth.ApiKey, shouldBeDefaultAuth.ApiKey);
 
 			OpenAI_API.APIAuthentication.Default = new OpenAI_API.APIAuthentication("pk-testAA");
 			api = new OpenAI_API.OpenAIAPI();
-			OpenAI_API.APIAuthentication shouldBeManualAuth = api.Auth;
+			OpenAI_API.IAPIAuthentication shouldBeManualAuth = api.Auth;
 			Assert.IsNotNull(shouldBeManualAuth);
 			Assert.IsNotNull(shouldBeManualAuth.ApiKey);
 			Assert.AreEqual(manualAuth.ApiKey, shouldBeManualAuth.ApiKey);