diff --git a/src/ModelContextProtocol.Core/Client/McpClientTool.cs b/src/ModelContextProtocol.Core/Client/McpClientTool.cs
index a3cf7a4..1810e9c 100644
--- a/src/ModelContextProtocol.Core/Client/McpClientTool.cs
+++ b/src/ModelContextProtocol.Core/Client/McpClientTool.cs
@@ -77,6 +77,9 @@ public sealed class McpClientTool : AIFunction
     /// <inheritdoc/>
     public override JsonElement JsonSchema => ProtocolTool.InputSchema;
 
+    /// <inheritdoc/>
+    public override JsonElement? ReturnJsonSchema => ProtocolTool.OutputSchema;
+
     /// <inheritdoc/>
     public override JsonSerializerOptions JsonSerializerOptions { get; }