Add request options bag to high level requests and include Meta

samples/EverythingServer/Program.cs

@@ -75,7 +75,7 @@ await ctx.Server.SampleAsync([
                 new ChatMessage(ChatRole.System, "You are a helpful test server"),
                 new ChatMessage(ChatRole.User, $"Resource {uri}, context: A new subscription was started"),
             ],
-            options: new ChatOptions
+            chatOptions: new ChatOptions
             {
                 MaxOutputTokens = 100,
                 Temperature = 0.7f,

samples/EverythingServer/Tools/SampleLlmTool.cs

@@ -15,7 +15,7 @@ public static async Task<string> SampleLLM(
         CancellationToken cancellationToken)
     {
         var samplingParams = CreateRequestSamplingParams(prompt ?? string.Empty, "sampleLLM", maxTokens);
-        var sampleResult = await server.SampleAsync(samplingParams, cancellationToken);
+        var sampleResult = await server.SampleAsync(samplingParams, cancellationToken: cancellationToken);
 
         return $"LLM sampling result: {sampleResult.Content.OfType<TextContentBlock>().FirstOrDefault()?.Text}";
     }

samples/TestServerWithHosting/Tools/SampleLlmTool.cs

@@ -18,7 +18,7 @@ public static async Task<string> SampleLLM(
         CancellationToken cancellationToken)
     {
         var samplingParams = CreateRequestSamplingParams(prompt ?? string.Empty, "sampleLLM", maxTokens);
-        var sampleResult = await thisServer.SampleAsync(samplingParams, cancellationToken);
+        var sampleResult = await thisServer.SampleAsync(samplingParams, cancellationToken: cancellationToken);
 
         return $"LLM sampling result: {sampleResult.Content.OfType<TextContentBlock>().FirstOrDefault()?.Text}";
     }

src/ModelContextProtocol.Core/Client/McpClientExtensions.cs

@@ -39,7 +39,7 @@ public static class McpClientExtensions
     [Obsolete($"Use {nameof(McpClient)}.{nameof(McpClient.PingAsync)} instead. This member will be removed in a subsequent release.")] // See: https://github.com/modelcontextprotocol/csharp-sdk/issues/774
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static Task PingAsync(this IMcpClient client, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).PingAsync(cancellationToken);
+        => AsClientOrThrow(client).PingAsync(null, cancellationToken).AsTask();
 
     /// <summary>
     /// Retrieves a list of available tools from the server.
@@ -86,7 +86,7 @@ public static ValueTask<IList<McpClientTool>> ListToolsAsync(
         this IMcpClient client,
         JsonSerializerOptions? serializerOptions = null,
         CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).ListToolsAsync(serializerOptions, cancellationToken);
+        => AsClientOrThrow(client).ListToolsAsync(new RequestOptions { JsonSerializerOptions = serializerOptions }, cancellationToken);
 
     /// <summary>
     /// Creates an enumerable for asynchronously enumerating all available tools from the server.
@@ -126,7 +126,7 @@ public static IAsyncEnumerable<McpClientTool> EnumerateToolsAsync(
         this IMcpClient client,
         JsonSerializerOptions? serializerOptions = null,
         CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).EnumerateToolsAsync(serializerOptions, cancellationToken);
+        => AsClientOrThrow(client).EnumerateToolsAsync(new RequestOptions { JsonSerializerOptions = serializerOptions }, cancellationToken);
 
     /// <summary>
     /// Retrieves a list of available prompts from the server.
@@ -149,7 +149,7 @@ public static IAsyncEnumerable<McpClientTool> EnumerateToolsAsync(
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static ValueTask<IList<McpClientPrompt>> ListPromptsAsync(
         this IMcpClient client, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).ListPromptsAsync(cancellationToken);
+        => AsClientOrThrow(client).ListPromptsAsync(null, cancellationToken);
 
     /// <summary>
     /// Creates an enumerable for asynchronously enumerating all available prompts from the server.
@@ -182,7 +182,7 @@ public static ValueTask<IList<McpClientPrompt>> ListPromptsAsync(
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static IAsyncEnumerable<McpClientPrompt> EnumeratePromptsAsync(
         this IMcpClient client, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).EnumeratePromptsAsync(cancellationToken);
+        => AsClientOrThrow(client).EnumeratePromptsAsync(null, cancellationToken);
 
     /// <summary>
     /// Retrieves a specific prompt from the MCP server.
@@ -217,7 +217,7 @@ public static ValueTask<GetPromptResult> GetPromptAsync(
         IReadOnlyDictionary<string, object?>? arguments = null,
         JsonSerializerOptions? serializerOptions = null,
         CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).GetPromptAsync(name, arguments, serializerOptions, cancellationToken);
+        => AsClientOrThrow(client).GetPromptAsync(name, arguments, new RequestOptions { JsonSerializerOptions = serializerOptions }, cancellationToken);
 
     /// <summary>
     /// Retrieves a list of available resource templates from the server.
@@ -240,7 +240,7 @@ public static ValueTask<GetPromptResult> GetPromptAsync(
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static ValueTask<IList<McpClientResourceTemplate>> ListResourceTemplatesAsync(
         this IMcpClient client, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).ListResourceTemplatesAsync(cancellationToken);
+        => AsClientOrThrow(client).ListResourceTemplatesAsync(null, cancellationToken);
 
     /// <summary>
     /// Creates an enumerable for asynchronously enumerating all available resource templates from the server.
@@ -273,7 +273,7 @@ public static ValueTask<IList<McpClientResourceTemplate>> ListResourceTemplatesA
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static IAsyncEnumerable<McpClientResourceTemplate> EnumerateResourceTemplatesAsync(
         this IMcpClient client, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).EnumerateResourceTemplatesAsync(cancellationToken);
+        => AsClientOrThrow(client).EnumerateResourceTemplatesAsync(null, cancellationToken);
 
     /// <summary>
     /// Retrieves a list of available resources from the server.
@@ -308,7 +308,7 @@ public static IAsyncEnumerable<McpClientResourceTemplate> EnumerateResourceTempl
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static ValueTask<IList<McpClientResource>> ListResourcesAsync(
         this IMcpClient client, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).ListResourcesAsync(cancellationToken);
+        => AsClientOrThrow(client).ListResourcesAsync(null, cancellationToken);
 
     /// <summary>
     /// Creates an enumerable for asynchronously enumerating all available resources from the server.
@@ -341,7 +341,7 @@ public static ValueTask<IList<McpClientResource>> ListResourcesAsync(
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static IAsyncEnumerable<McpClientResource> EnumerateResourcesAsync(
         this IMcpClient client, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).EnumerateResourcesAsync(cancellationToken);
+        => AsClientOrThrow(client).EnumerateResourcesAsync(null, cancellationToken);
 
     /// <summary>
     /// Reads a resource from the server.
@@ -356,7 +356,7 @@ public static IAsyncEnumerable<McpClientResource> EnumerateResourcesAsync(
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static ValueTask<ReadResourceResult> ReadResourceAsync(
         this IMcpClient client, string uri, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).ReadResourceAsync(uri, cancellationToken);
+        => AsClientOrThrow(client).ReadResourceAsync(uri, null, cancellationToken);
 
     /// <summary>
     /// Reads a resource from the server.
@@ -370,7 +370,7 @@ public static ValueTask<ReadResourceResult> ReadResourceAsync(
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static ValueTask<ReadResourceResult> ReadResourceAsync(
         this IMcpClient client, Uri uri, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).ReadResourceAsync(uri, cancellationToken);
+        => AsClientOrThrow(client).ReadResourceAsync(uri, null, cancellationToken);
 
     /// <summary>
     /// Reads a resource from the server.
@@ -386,7 +386,7 @@ public static ValueTask<ReadResourceResult> ReadResourceAsync(
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static ValueTask<ReadResourceResult> ReadResourceAsync(
         this IMcpClient client, string uriTemplate, IReadOnlyDictionary<string, object?> arguments, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).ReadResourceAsync(uriTemplate, arguments, cancellationToken);
+        => AsClientOrThrow(client).ReadResourceAsync(uriTemplate, arguments, null, cancellationToken);
 
     /// <summary>
     /// Requests completion suggestions for a prompt argument or resource reference.
@@ -450,7 +450,7 @@ public static ValueTask<CompleteResult> CompleteAsync(this IMcpClient client, Re
     [Obsolete($"Use {nameof(McpClient)}.{nameof(McpClient.SubscribeToResourceAsync)} instead. This member will be removed in a subsequent release.")] // See: https://github.com/modelcontextprotocol/csharp-sdk/issues/774
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static Task SubscribeToResourceAsync(this IMcpClient client, string uri, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).SubscribeToResourceAsync(uri, cancellationToken);
+        => AsClientOrThrow(client).SubscribeToResourceAsync(uri, null, cancellationToken);
 
     /// <summary>
     /// Subscribes to a resource on the server to receive notifications when it changes.
@@ -479,7 +479,7 @@ public static Task SubscribeToResourceAsync(this IMcpClient client, string uri,
     [Obsolete($"Use {nameof(McpClient)}.{nameof(McpClient.SubscribeToResourceAsync)} instead. This member will be removed in a subsequent release.")] // See: https://github.com/modelcontextprotocol/csharp-sdk/issues/774
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static Task SubscribeToResourceAsync(this IMcpClient client, Uri uri, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).SubscribeToResourceAsync(uri, cancellationToken);
+        => AsClientOrThrow(client).SubscribeToResourceAsync(uri, null, cancellationToken);
 
     /// <summary>
     /// Unsubscribes from a resource on the server to stop receiving notifications about its changes.
@@ -508,7 +508,7 @@ public static Task SubscribeToResourceAsync(this IMcpClient client, Uri uri, Can
     [Obsolete($"Use {nameof(McpClient)}.{nameof(McpClient.UnsubscribeFromResourceAsync)} instead. This member will be removed in a subsequent release.")] // See: https://github.com/modelcontextprotocol/csharp-sdk/issues/774
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static Task UnsubscribeFromResourceAsync(this IMcpClient client, string uri, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).UnsubscribeFromResourceAsync(uri, cancellationToken);
+        => AsClientOrThrow(client).UnsubscribeFromResourceAsync(uri, null, cancellationToken);
 
     /// <summary>
     /// Unsubscribes from a resource on the server to stop receiving notifications about its changes.
@@ -536,7 +536,7 @@ public static Task UnsubscribeFromResourceAsync(this IMcpClient client, string u
     [Obsolete($"Use {nameof(McpClient)}.{nameof(McpClient.UnsubscribeFromResourceAsync)} instead. This member will be removed in a subsequent release.")] // See: https://github.com/modelcontextprotocol/csharp-sdk/issues/774
     [EditorBrowsable(EditorBrowsableState.Never)]
     public static Task UnsubscribeFromResourceAsync(this IMcpClient client, Uri uri, CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).UnsubscribeFromResourceAsync(uri, cancellationToken);
+        => AsClientOrThrow(client).UnsubscribeFromResourceAsync(uri, null, cancellationToken);
 
     /// <summary>
     /// Invokes a tool on the server.
@@ -582,7 +582,7 @@ public static ValueTask<CallToolResult> CallToolAsync(
         IProgress<ProgressNotificationValue>? progress = null,
         JsonSerializerOptions? serializerOptions = null,
         CancellationToken cancellationToken = default)
-        => AsClientOrThrow(client).CallToolAsync(toolName, arguments, progress, serializerOptions, cancellationToken);
+        => AsClientOrThrow(client).CallToolAsync(toolName, arguments, progress, new RequestOptions { JsonSerializerOptions = serializerOptions }, cancellationToken);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
 #pragma warning disable CS0618 // Type or member is obsolete

src/ModelContextProtocol.Core/Client/McpClientPrompt.cs

@@ -97,6 +97,6 @@ public async ValueTask<GetPromptResult> GetAsync(
             arguments as IReadOnlyDictionary<string, object?> ??
             arguments?.ToDictionary();
 
-        return await _client.GetPromptAsync(ProtocolPrompt.Name, argDict, serializerOptions, cancellationToken: cancellationToken).ConfigureAwait(false);
+        return await _client.GetPromptAsync(ProtocolPrompt.Name, argDict, new RequestOptions() { JsonSerializerOptions = serializerOptions }, cancellationToken).ConfigureAwait(false);
     }
 }

src/ModelContextProtocol.Core/Client/McpClientResource.cs

@@ -79,10 +79,10 @@ public McpClientResource(McpClient client, Resource resource)
     /// <returns>A <see cref="ValueTask{ReadResourceResult}"/> containing the resource's result with content and messages.</returns>
     /// <remarks>
     /// <para>
-    /// This is a convenience method that internally calls <see cref="McpClient.ReadResourceAsync(string, CancellationToken)"/>.
+    /// This is a convenience method that internally calls <see cref="McpClient.ReadResourceAsync(string, RequestOptions, CancellationToken)"/>.
     /// </para>
     /// </remarks>
     public ValueTask<ReadResourceResult> ReadAsync(
         CancellationToken cancellationToken = default) =>
-        _client.ReadResourceAsync(Uri, cancellationToken);
+        _client.ReadResourceAsync(Uri, cancellationToken: cancellationToken);
 }

src/ModelContextProtocol.Core/Client/McpClientResourceTemplate.cs

@@ -84,5 +84,5 @@ public McpClientResourceTemplate(McpClient client, ResourceTemplate resourceTemp
     public ValueTask<ReadResourceResult> ReadAsync(
         IReadOnlyDictionary<string, object?> arguments,
         CancellationToken cancellationToken = default) =>
-        _client.ReadResourceAsync(UriTemplate, arguments, cancellationToken);
+        _client.ReadResourceAsync(UriTemplate, arguments, cancellationToken: cancellationToken);
 }

src/ModelContextProtocol.Core/Client/McpClientTool.cs

@@ -128,7 +128,11 @@ internal McpClientTool(
     protected async override ValueTask<object?> InvokeCoreAsync(
         AIFunctionArguments arguments, CancellationToken cancellationToken)
     {
-        CallToolResult result = await CallAsync(arguments, _progress, JsonSerializerOptions, cancellationToken).ConfigureAwait(false);
+        var options = JsonSerializerOptions is null ? null : new RequestOptions()
+        {
+            JsonSerializerOptions = JsonSerializerOptions,
+        };
+        CallToolResult result = await CallAsync(arguments, _progress, options, cancellationToken).ConfigureAwait(false);
 
         // We want to translate the result content into AIContent, using AIContent as the exchange types, so
         // that downstream IChatClients can specialize handling based on the content (e.g. sending image content
@@ -163,8 +167,8 @@ result.StructuredContent is null &&
     /// value will result in a progress token being included in the call, and any resulting progress notifications during the operation
     /// routed to this instance.
     /// </param>
-    /// <param name="serializerOptions">
-    /// The JSON serialization options governing argument serialization. If <see langword="null"/>, the default serialization options are used.
+    /// <param name="options">
+    /// Optional request options including metadata, serialization settings, and progress tracking.
     /// </param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>
@@ -191,9 +195,16 @@ result.StructuredContent is null &&
     public ValueTask<CallToolResult> CallAsync(
         IReadOnlyDictionary<string, object?>? arguments = null,
         IProgress<ProgressNotificationValue>? progress = null,
-        JsonSerializerOptions? serializerOptions = null,
+        RequestOptions? options = null,
         CancellationToken cancellationToken = default) =>
-        _client.CallToolAsync(ProtocolTool.Name, arguments, progress, serializerOptions, cancellationToken);
+        _client.CallToolAsync(
+            ProtocolTool.Name,
+            arguments,
+            progress,
+            options ?? new RequestOptions() {
+                JsonSerializerOptions = JsonSerializerOptions
+            },
+            cancellationToken);
 
     /// <summary>
     /// Creates a new instance of the tool but modified to return the specified name from its <see cref="Name"/> property.

src/ModelContextProtocol.Core/McpEndpointExtensions.cs

@@ -126,7 +126,7 @@ public static Task NotifyProgressAsync(
         ProgressToken progressToken,
         ProgressNotificationValue progress,
         CancellationToken cancellationToken = default)
-        => AsSessionOrThrow(endpoint).NotifyProgressAsync(progressToken, progress, cancellationToken);
+        => AsSessionOrThrow(endpoint).NotifyProgressAsync(progressToken, progress, cancellationToken: cancellationToken);
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
 #pragma warning disable CS0618 // Type or member is obsolete

src/ModelContextProtocol.Core/McpJsonUtilities.cs

@@ -132,6 +132,7 @@ internal static bool IsValidMcpToolSchema(JsonElement element)
     [JsonSerializable(typeof(ListRootsResult))]
     [JsonSerializable(typeof(ListToolsRequestParams))]
     [JsonSerializable(typeof(ListToolsResult))]
+    [JsonSerializable(typeof(PingRequestParams))]
     [JsonSerializable(typeof(PingResult))]
     [JsonSerializable(typeof(ReadResourceRequestParams))]
     [JsonSerializable(typeof(ReadResourceResult))]

src/ModelContextProtocol.Core/McpSession.Methods.cs

@@ -152,6 +152,7 @@ internal Task SendNotificationAsync<TParameters>(
     /// </summary>
     /// <param name="progressToken">The token that identifies the operation for which progress is being reported.</param>
     /// <param name="progress">The progress update to send, containing information such as percentage complete or status message.</param>
+    /// <param name="options">Optional request options including metadata, serialization settings, and progress tracking.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>A task representing the completion of the notification operation (not the operation being tracked).</returns>
     /// <exception cref="ArgumentNullException">The current session instance is <see langword="null"/>.</exception>
@@ -168,6 +169,7 @@ internal Task SendNotificationAsync<TParameters>(
     public Task NotifyProgressAsync(
         ProgressToken progressToken,
         ProgressNotificationValue progress,
+        RequestOptions? options = null,
         CancellationToken cancellationToken = default)
     {
         return SendNotificationAsync(
@@ -176,6 +178,7 @@ public Task NotifyProgressAsync(
             {
                 ProgressToken = progressToken,
                 Progress = progress,
+                Meta = options?.Meta,
             },
             McpJsonUtilities.JsonContext.Default.ProgressNotificationParams,
             cancellationToken);

src/ModelContextProtocol.Core/Protocol/PingRequestParams.cs

@@ -0,0 +1,11 @@
+namespace ModelContextProtocol.Protocol;
+
+/// <summary>
+/// Represents the parameters used with a <see cref="RequestMethods.Ping"/> request to verify
+/// server connectivity.
+/// </summary>
+/// <remarks>
+/// The server responds with a <see cref="PingResult"/>.
+/// See the <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/">schema</see> for details.
+/// </remarks>
+public sealed class PingRequestParams : RequestParams;