diff --git a/src/ModelContextProtocol.Core/Server/AIFunctionMcpServerPrompt.cs b/src/ModelContextProtocol.Core/Server/AIFunctionMcpServerPrompt.cs
index c755cd9e5..d9073d4b5 100644
--- a/src/ModelContextProtocol.Core/Server/AIFunctionMcpServerPrompt.cs
+++ b/src/ModelContextProtocol.Core/Server/AIFunctionMcpServerPrompt.cs
@@ -177,6 +177,13 @@ private static McpServerPromptCreateOptions DeriveOptions(MethodInfo method, Mcp
/// Gets the wrapped by this prompt.
internal AIFunction AIFunction { get; }
+ /// Backing cache for .
+ private object? _allowedValueCompletions;
+
+ /// Gets the values that each restricted parameter of the prompt allows, or if none are restricted.
+ internal Dictionary? AllowedValueCompletions =>
+ Server.AllowedValueCompletions.GetOrCreate(ref _allowedValueCompletions, AIFunction.JsonSchema);
+
/// Initializes a new instance of the class.
private AIFunctionMcpServerPrompt(AIFunction function, Prompt prompt, IReadOnlyList