diff --git a/src/Mscc.GenerativeAI/CHANGELOG.md b/src/Mscc.GenerativeAI/CHANGELOG.md
index 7a20216..ca1cd99 100644
--- a/src/Mscc.GenerativeAI/CHANGELOG.md
+++ b/src/Mscc.GenerativeAI/CHANGELOG.md
@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - compatibility methods for PaLM models
+- Feature suggestion: Retry mechanism ([#2](https://github.com/mscraftsman/generative-ai/issues/2))
 
 ### Changed
 ### Fixed
@@ -19,6 +20,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - missing comments and better explanations
+- add GoogleAI type ([#3](https://github.com/mscraftsman/generative-ai/issues/3))
+- read environment variables in GoogleAI and VertexAI
 
 ## 0.8.3
 
diff --git a/src/Mscc.GenerativeAI/GoogleAI.cs b/src/Mscc.GenerativeAI/GoogleAI.cs
index c03c978..db42a31 100644
--- a/src/Mscc.GenerativeAI/GoogleAI.cs
+++ b/src/Mscc.GenerativeAI/GoogleAI.cs
@@ -18,6 +18,8 @@ public sealed class GoogleAI
         /// </summary>
         private GoogleAI()
         {
+            GenerativeModelExtensions.ReadDotEnv();
+
             _apiKey = Environment.GetEnvironmentVariable("GOOGLE_API_KEY");
         }
         
diff --git a/src/Mscc.GenerativeAI/VertexAI.cs b/src/Mscc.GenerativeAI/VertexAI.cs
index 2eacad8..fc3bcd0 100644
--- a/src/Mscc.GenerativeAI/VertexAI.cs
+++ b/src/Mscc.GenerativeAI/VertexAI.cs
@@ -1,35 +1,57 @@
-using System.Collections.Generic;
+#if NET472_OR_GREATER || NETSTANDARD2_0
+using System;
+using System.Collections.Generic;
+#endif
 
 namespace Mscc.GenerativeAI
 {
-    public class VertexAI
+    /// <summary>
+    /// Entry point to access Gemini API running in Vertex AI.
+    /// </summary>
+    public sealed class VertexAI
     {
-        private readonly string projectId;
-        private readonly string region;
+        private readonly string? _projectId;
+        private readonly string _region = "us-central1";
 
+        /// <summary>
+        /// Default constructor attempts to read environment variables and
+        /// sets default values, if available
+        /// </summary>
+        private VertexAI()
+        {
+            GenerativeModelExtensions.ReadDotEnv();
+
+            _projectId = Environment.GetEnvironmentVariable("GOOGLE_PROJECT_ID");
+            _region = Environment.GetEnvironmentVariable("GOOGLE_REGION") ?? _region;
+        }
+        
         /// <summary>
         /// Constructor to initialize access to Vertex AI Gemini API.
         /// </summary>
         /// <param name="projectId">Identifier of the Google Cloud project</param>
         /// <param name="region">Region to use</param>
-        public VertexAI(string projectId, string region)
+        public VertexAI(string projectId, string region) : this()
         {
-            this.projectId = projectId;
-            this.region = region;
+            _projectId ??= projectId;
+            _region ??= region;
         }
 
         /// <summary>
         /// Create a generative model on Vertex AI to use.
         /// </summary>
         /// <param name="model">Model to use (default: "gemini-1.0-pro")</param>
-        /// <param name="generationConfig"></param>
-        /// <param name="safetySettings"></param>
+        /// <param name="generationConfig">Optional. Configuration options for model generation and outputs.</param>
+        /// <param name="safetySettings">Optional. A list of unique SafetySetting instances for blocking unsafe content.</param>
+        /// <exception cref="ArgumentNullException"></exception>
         /// <returns></returns>
         public GenerativeModel GenerativeModel(string model = Model.Gemini10Pro,
             GenerationConfig? generationConfig = null,
             List<SafetySetting>? safetySettings = null)
         {
-            return new GenerativeModel(projectId, region, model, generationConfig, safetySettings);
+            if (_projectId is null) throw new ArgumentNullException("projectId");
+            if (_region is null) throw new ArgumentNullException("region");
+
+            return new GenerativeModel(_projectId, _region, model, generationConfig, safetySettings);
         }
     }
 }