Make Name and Value constructor parameters in McpMetaAttribute and check AIFunction.Metadata.UnderlyingMethod

Co-authored-by: stephentoub <[email protected]>

Author: Copilot

samples/AspNetCoreMcpServer/Tools/WeatherTools.cs

@@ -17,8 +17,8 @@ public WeatherTools(IHttpClientFactory httpClientFactory)
     }
 
     [McpServerTool, Description("Get weather alerts for a US state.")]
-    [McpMeta(Name = "category", Value = "weather")]
-    [McpMeta(Name = "dataSource", Value = "weather.gov")]
+    [McpMeta("category", "weather")]
+    [McpMeta("dataSource", "weather.gov")]
     public async Task<string> GetAlerts(
         [Description("The US state to get alerts for. Use the 2 letter abbreviation for the state (e.g. NY).")] string state)
     {
@@ -48,8 +48,8 @@ public async Task<string> GetAlerts(
     }
 
     [McpServerTool, Description("Get weather forecast for a location.")]
-    [McpMeta(Name = "category", Value = "weather")]
-    [McpMeta(Name = "recommendedModel", Value = "gpt-4")]
+    [McpMeta("category", "weather")]
+    [McpMeta("recommendedModel", "gpt-4")]
     public async Task<string> GetForecast(
         [Description("Latitude of the location.")] double latitude,
         [Description("Longitude of the location.")] double longitude)

src/ModelContextProtocol.Core/Server/AIFunctionMcpServerPrompt.cs

@@ -139,10 +139,11 @@ private static AIFunctionFactoryOptions CreateAIFunctionFactoryOptions(
             Icons = options?.Icons,
         };
 
-        // Populate Meta from options and/or McpMetaAttribute instances if a MethodInfo is in the metadata
-        if (options?.Metadata?.FirstOrDefault(m => m is MethodInfo) is MethodInfo method)
+        // Populate Meta from options and/or McpMetaAttribute instances if a MethodInfo is available
+        MethodInfo? method = options?.Metadata?.FirstOrDefault(m => m is MethodInfo) as MethodInfo ?? function.Metadata?.UnderlyingMethod;
+        if (method is not null)
         {
-            prompt.Meta = AIFunctionMcpServerTool.CreateMetaFromAttributes(method, options.Meta);
+            prompt.Meta = AIFunctionMcpServerTool.CreateMetaFromAttributes(method, options?.Meta);
         }
         else if (options?.Meta is not null)
         {

src/ModelContextProtocol.Core/Server/AIFunctionMcpServerResource.cs

@@ -212,11 +212,12 @@ private static AIFunctionFactoryOptions CreateAIFunctionFactoryOptions(
 
         string name = options?.Name ?? function.Name;
 
-        // Populate Meta from options and/or McpMetaAttribute instances if a MethodInfo is in the metadata
+        // Populate Meta from options and/or McpMetaAttribute instances if a MethodInfo is available
+        MethodInfo? method = options?.Metadata?.FirstOrDefault(m => m is MethodInfo) as MethodInfo ?? function.Metadata?.UnderlyingMethod;
         JsonObject? meta = null;
-        if (options?.Metadata?.FirstOrDefault(m => m is MethodInfo) is MethodInfo method)
+        if (method is not null)
         {
-            meta = AIFunctionMcpServerTool.CreateMetaFromAttributes(method, options.Meta);
+            meta = AIFunctionMcpServerTool.CreateMetaFromAttributes(method, options?.Meta);
         }
         else if (options?.Meta is not null)
         {

src/ModelContextProtocol.Core/Server/AIFunctionMcpServerTool.cs

@@ -144,8 +144,9 @@ options.OpenWorld is not null ||
                 };
             }
 
-            // Populate Meta from options and/or McpMetaAttribute instances if a MethodInfo is in the metadata
-            if (options.Metadata?.FirstOrDefault(m => m is MethodInfo) is MethodInfo method)
+            // Populate Meta from options and/or McpMetaAttribute instances if a MethodInfo is available
+            MethodInfo? method = options.Metadata?.FirstOrDefault(m => m is MethodInfo) as MethodInfo ?? function.Metadata?.UnderlyingMethod;
+            if (method is not null)
             {
                 tool.Meta = CreateMetaFromAttributes(method, options.Meta);
             }

src/ModelContextProtocol.Core/Server/McpMetaAttribute.cs

@@ -18,8 +18,8 @@ namespace ModelContextProtocol.Server;
 /// <example>
 /// <code>
 /// [McpServerTool]
-/// [McpMeta(Name = "model", Value = "gpt-4o")]
-/// [McpMeta(Name = "version", Value = "1.0")]
+/// [McpMeta("model", "gpt-4o")]
+/// [McpMeta("version", "1.0")]
 /// public string MyTool(string input)
 /// {
 ///     return $"Processed: {input}";
@@ -33,26 +33,30 @@ public sealed class McpMetaAttribute : Attribute
     /// <summary>
     /// Initializes a new instance of the <see cref="McpMetaAttribute"/> class.
     /// </summary>
-    public McpMetaAttribute()
+    /// <param name="name">The name (key) of the metadata entry.</param>
+    /// <param name="value">The value of the metadata entry.</param>
+    public McpMetaAttribute(string name, string value)
     {
+        Name = name;
+        Value = value;
     }
 
     /// <summary>
-    /// Gets or sets the name (key) of the metadata entry.
+    /// Gets the name (key) of the metadata entry.
     /// </summary>
     /// <remarks>
     /// This value is used as the key in the metadata object. It should be a unique identifier
     /// for this piece of metadata within the context of the primitive.
     /// </remarks>
-    public required string Name { get; set; }
+    public string Name { get; }
 
     /// <summary>
-    /// Gets or sets the value of the metadata entry.
+    /// Gets the value of the metadata entry.
     /// </summary>
     /// <remarks>
     /// This value is stored as a string in the metadata object. For complex values, use the
     /// <see cref="McpServerToolCreateOptions.Meta"/>, <see cref="McpServerPromptCreateOptions.Meta"/>, 
     /// or <see cref="McpServerResourceCreateOptions.Meta"/> property to provide a JsonObject directly.
     /// </remarks>
-    public required string Value { get; set; }
+    public string Value { get; }
 }

tests/ModelContextProtocol.Tests/Server/McpMetaAttributeTests.cs

@@ -178,8 +178,8 @@ public void McpMetaAttribute_ResourceOptionsMetaTakesPrecedence()
     private class TestToolClass
     {
         [McpServerTool]
-        [McpMeta(Name = "model", Value = "gpt-4o")]
-        [McpMeta(Name = "version", Value = "1.0")]
+        [McpMeta("model", "gpt-4o")]
+        [McpMeta("version", "1.0")]
         public static string ToolWithMeta(string input)
         {
             return input;
@@ -192,7 +192,7 @@ public static string ToolWithoutMeta(string input)
         }
 
         [McpServerTool]
-        [McpMeta(Name = "test-key", Value = "test-value")]
+        [McpMeta("test-key", "test-value")]
         public static string ToolWithSingleMeta(string input)
         {
             return input;
@@ -202,8 +202,8 @@ public static string ToolWithSingleMeta(string input)
     private class TestPromptClass
     {
         [McpServerPrompt]
-        [McpMeta(Name = "type", Value = "reasoning")]
-        [McpMeta(Name = "model", Value = "claude-3")]
+        [McpMeta("type", "reasoning")]
+        [McpMeta("model", "claude-3")]
         public static string PromptWithMeta(string input)
         {
             return input;
@@ -213,8 +213,8 @@ public static string PromptWithMeta(string input)
     private class TestResourceClass
     {
         [McpServerResource(UriTemplate = "resource://test/{id}")]
-        [McpMeta(Name = "encoding", Value = "text/plain")]
-        [McpMeta(Name = "caching", Value = "cached")]
+        [McpMeta("encoding", "text/plain")]
+        [McpMeta("caching", "cached")]
         public static string ResourceWithMeta(string id)
         {
             return $"Resource content for {id}";