Add configurable default for sampling MaxTokens

src/ModelContextProtocol.Core/Server/McpServer.Methods.cs

@@ -153,7 +153,7 @@ public async Task<ChatResponse> SampleAsync(
         var result = await SampleAsync(new()
         {
             Messages = samplingMessages,
-            MaxTokens = options?.MaxOutputTokens ?? int.MaxValue,
+            MaxTokens = options?.MaxOutputTokens ?? ServerOptions.DefaultSamplingMaxTokens,
             StopSequences = options?.StopSequences?.ToArray(),
             SystemPrompt = systemPrompt?.ToString(),
             Temperature = options?.Temperature,

src/ModelContextProtocol.Core/Server/McpServerOptions.cs

@@ -152,4 +152,21 @@ public McpServerHandlers Handlers
     /// </para>
     /// </remarks>
     public McpServerPrimitiveCollection<McpServerPrompt>? PromptCollection { get; set; }
+
+    /// <summary>
+    /// Gets or sets the default maximum number of tokens to use for sampling requests when not explicitly specified.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This value is used as the <c>maxTokens</c> parameter in sampling requests to the client when the 
+    /// <see cref="Microsoft.Extensions.AI.ChatOptions.MaxOutputTokens"/> property is not set in the request options.
+    /// The MCP protocol requires a <c>maxTokens</c> value for all sampling requests.
+    /// </para>
+    /// <para>
+    /// The default value is 1000 tokens, which provides a reasonable balance between allowing meaningful 
+    /// responses and preventing excessive token usage. This value should be set based on your application's 
+    /// requirements and the capabilities of the LLM being used by the client.
+    /// </para>
+    /// </remarks>
+    public int DefaultSamplingMaxTokens { get; set; } = 1000;
 }

tests/ModelContextProtocol.Tests/Server/McpServerExtensionsTests.cs

@@ -129,6 +129,10 @@ public async Task SampleAsync_Messages_Forwards_To_McpServer_SendRequestAsync()
             .Setup(s => s.ClientCapabilities)
             .Returns(new ClientCapabilities() { Sampling = new() });
 
+        mockServer
+            .Setup(s => s.ServerOptions)
+            .Returns(new McpServerOptions());
+
         mockServer
             .Setup(s => s.SendRequestAsync(It.IsAny<JsonRpcRequest>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(new JsonRpcResponse