diff --git a/src/AnthropicClient/Models/ContentType.cs b/src/AnthropicClient/Models/ContentType.cs
index e34013c..b84fb21 100644
--- a/src/AnthropicClient/Models/ContentType.cs
+++ b/src/AnthropicClient/Models/ContentType.cs
@@ -24,4 +24,9 @@ public static class ContentType
   /// Represents the tool result content type.
   /// </summary>
   public const string ToolResult = "tool_result";
+
+  /// <summary>
+  /// Represents the document content type.
+  /// </summary>
+  public const string Document = "document";
 }
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/ContentTypeTests.cs b/tests/AnthropicClient.Tests/Unit/Models/ContentTypeTests.cs
index 51362fb..d072118 100644
--- a/tests/AnthropicClient.Tests/Unit/Models/ContentTypeTests.cs
+++ b/tests/AnthropicClient.Tests/Unit/Models/ContentTypeTests.cs
@@ -5,40 +5,30 @@ public class ContentTypeTests
   [Fact]
   public void Text_WhenCalled_ItShouldReturnText()
   {
-    var expected = "text";
-
-    var actual = ContentType.Text;
-
-    actual.Should().Be(expected);
+    ContentType.Text.Should().Be("text");
   }
 
   [Fact]
   public void Image_WhenCalled_ItShouldReturnImage()
   {
-    var expected = "image";
-
-    var actual = ContentType.Image;
-
-    actual.Should().Be(expected);
+    ContentType.Image.Should().Be("image");
   }
 
   [Fact]
   public void ToolUse_WhenCalled_ItShouldReturnToolUse()
   {
-    var expected = "tool_use";
-
-    var actual = ContentType.ToolUse;
-
-    actual.Should().Be(expected);
+    ContentType.ToolUse.Should().Be("tool_use");
   }
 
   [Fact]
   public void ToolResult_WhenCalled_ItShouldReturnToolResult()
   {
-    var expected = "tool_result";
+    ContentType.ToolResult.Should().Be("tool_result");
+  }
 
-    var actual = ContentType.ToolResult;
-
-    actual.Should().Be(expected);
+  [Fact]
+  public void Document_WhenCalled_ItShouldReturnDocument()
+  {
+    ContentType.Document.Should().Be("document");
   }
 }
\ No newline at end of file