Remove server back-references from protocol DTO types (#1345)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>
Co-authored-by: Stephen Toub <stoub@microsoft.com>

src/ModelContextProtocol.AspNetCore/AuthorizationFilterSetup.cs

@@ -43,31 +43,39 @@ internal sealed class AuthorizationFilterSetup(IAuthorizationPolicyProvider? pol
 
     private void ConfigureListToolsFilter(McpServerOptions options)
     {
-        options.Filters.Request.ListToolsFilters.Add(next => async (context, cancellationToken) =>
+        options.Filters.Request.ListToolsFilters.Add(next =>
         {
-            context.Items[AuthorizationFilterInvokedKey] = true;
+            var toolCollection = options.ToolCollection;
+            return async (context, cancellationToken) =>
+            {
+                context.Items[AuthorizationFilterInvokedKey] = true;
 
-            var result = await next(context, cancellationToken);
-            await FilterAuthorizedItemsAsync(
-                result.Tools, static tool => tool.McpServerTool,
-                context.User, context.Services, context);
-            return result;
+                var result = await next(context, cancellationToken);
+                await FilterAuthorizedItemsAsync(
+                    result.Tools, tool => toolCollection is not null && toolCollection.TryGetPrimitive(tool.Name, out var serverTool) ? serverTool : null,
+                    context.User, context.Services, context);
+                return result;
+            };
         });
     }
 
     private static void CheckListToolsFilter(McpServerOptions options)
     {
-        options.Filters.Request.ListToolsFilters.Add(next => async (context, cancellationToken) =>
+        options.Filters.Request.ListToolsFilters.Add(next =>
         {
-            var result = await next(context, cancellationToken);
-
-            if (HasAuthorizationMetadata(result.Tools.Select(static tool => tool.McpServerTool))
-                && !context.Items.ContainsKey(AuthorizationFilterInvokedKey))
+            var toolCollection = options.ToolCollection;
+            return async (context, cancellationToken) =>
             {
-                throw new InvalidOperationException("Authorization filter was not invoked for tools/list operation, but authorization metadata was found on the tools. Ensure that AddAuthorizationFilters() is called on the IMcpServerBuilder to configure authorization filters.");
-            }
+                var result = await next(context, cancellationToken);
 
-            return result;
+                if (HasAuthorizationMetadata(result.Tools.Select(tool => toolCollection is not null && toolCollection.TryGetPrimitive(tool.Name, out var serverTool) ? serverTool : null))
+                    && !context.Items.ContainsKey(AuthorizationFilterInvokedKey))
+                {
+                    throw new InvalidOperationException("Authorization filter was not invoked for tools/list operation, but authorization metadata was found on the tools. Ensure that AddAuthorizationFilters() is called on the IMcpServerBuilder to configure authorization filters.");
+                }
+
+                return result;
+            };
         });
     }
 
@@ -103,61 +111,77 @@ internal sealed class AuthorizationFilterSetup(IAuthorizationPolicyProvider? pol
 
     private void ConfigureListResourcesFilter(McpServerOptions options)
     {
-        options.Filters.Request.ListResourcesFilters.Add(next => async (context, cancellationToken) =>
+        options.Filters.Request.ListResourcesFilters.Add(next =>
         {
-            context.Items[AuthorizationFilterInvokedKey] = true;
+            var resourceCollection = options.ResourceCollection;
+            return async (context, cancellationToken) =>
+            {
+                context.Items[AuthorizationFilterInvokedKey] = true;
 
-            var result = await next(context, cancellationToken);
-            await FilterAuthorizedItemsAsync(
-                result.Resources, static resource => resource.McpServerResource,
-                context.User, context.Services, context);
-            return result;
+                var result = await next(context, cancellationToken);
+                await FilterAuthorizedItemsAsync(
+                    result.Resources, resource => resourceCollection is not null && resourceCollection.TryGetPrimitive(resource.Uri, out var serverResource) ? serverResource : null,
+                    context.User, context.Services, context);
+                return result;
+            };
         });
     }
 
     private static void CheckListResourcesFilter(McpServerOptions options)
     {
-        options.Filters.Request.ListResourcesFilters.Add(next => async (context, cancellationToken) =>
+        options.Filters.Request.ListResourcesFilters.Add(next =>
         {
-            var result = await next(context, cancellationToken);
-
-            if (HasAuthorizationMetadata(result.Resources.Select(static resource => resource.McpServerResource))
-                && !context.Items.ContainsKey(AuthorizationFilterInvokedKey))
+            var resourceCollection = options.ResourceCollection;
+            return async (context, cancellationToken) =>
             {
-                throw new InvalidOperationException("Authorization filter was not invoked for resources/list operation, but authorization metadata was found on the resources. Ensure that AddAuthorizationFilters() is called on the IMcpServerBuilder to configure authorization filters.");
-            }
+                var result = await next(context, cancellationToken);
 
-            return result;
+                if (HasAuthorizationMetadata(result.Resources.Select(resource => resourceCollection is not null && resourceCollection.TryGetPrimitive(resource.Uri, out var serverResource) ? serverResource : null))
+                    && !context.Items.ContainsKey(AuthorizationFilterInvokedKey))
+                {
+                    throw new InvalidOperationException("Authorization filter was not invoked for resources/list operation, but authorization metadata was found on the resources. Ensure that AddAuthorizationFilters() is called on the IMcpServerBuilder to configure authorization filters.");
+                }
+
+                return result;
+            };
         });
     }
 
     private void ConfigureListResourceTemplatesFilter(McpServerOptions options)
     {
-        options.Filters.Request.ListResourceTemplatesFilters.Add(next => async (context, cancellationToken) =>
+        options.Filters.Request.ListResourceTemplatesFilters.Add(next =>
         {
-            context.Items[AuthorizationFilterInvokedKey] = true;
+            var resourceCollection = options.ResourceCollection;
+            return async (context, cancellationToken) =>
+            {
+                context.Items[AuthorizationFilterInvokedKey] = true;
 
-            var result = await next(context, cancellationToken);
-            await FilterAuthorizedItemsAsync(
-                result.ResourceTemplates, static resourceTemplate => resourceTemplate.McpServerResource,
-                context.User, context.Services, context);
-            return result;
+                var result = await next(context, cancellationToken);
+                await FilterAuthorizedItemsAsync(
+                    result.ResourceTemplates, resourceTemplate => resourceCollection is not null && resourceCollection.TryGetPrimitive(resourceTemplate.UriTemplate, out var serverResource) ? serverResource : null,
+                    context.User, context.Services, context);
+                return result;
+            };
         });
     }
 
     private static void CheckListResourceTemplatesFilter(McpServerOptions options)
     {
-        options.Filters.Request.ListResourceTemplatesFilters.Add(next => async (context, cancellationToken) =>
+        options.Filters.Request.ListResourceTemplatesFilters.Add(next =>
         {
-            var result = await next(context, cancellationToken);
-
-            if (HasAuthorizationMetadata(result.ResourceTemplates.Select(static resourceTemplate => resourceTemplate.McpServerResource))
-                && !context.Items.ContainsKey(AuthorizationFilterInvokedKey))
+            var resourceCollection = options.ResourceCollection;
+            return async (context, cancellationToken) =>
             {
-                throw new InvalidOperationException("Authorization filter was not invoked for resources/templates/list operation, but authorization metadata was found on the resource templates. Ensure that AddAuthorizationFilters() is called on the IMcpServerBuilder to configure authorization filters.");
-            }
+                var result = await next(context, cancellationToken);
 
-            return result;
+                if (HasAuthorizationMetadata(result.ResourceTemplates.Select(resourceTemplate => resourceCollection is not null && resourceCollection.TryGetPrimitive(resourceTemplate.UriTemplate, out var serverResource) ? serverResource : null))
+                    && !context.Items.ContainsKey(AuthorizationFilterInvokedKey))
+                {
+                    throw new InvalidOperationException("Authorization filter was not invoked for resources/templates/list operation, but authorization metadata was found on the resource templates. Ensure that AddAuthorizationFilters() is called on the IMcpServerBuilder to configure authorization filters.");
+                }
+
+                return result;
+            };
         });
     }
 
@@ -193,31 +217,39 @@ internal sealed class AuthorizationFilterSetup(IAuthorizationPolicyProvider? pol
 
     private void ConfigureListPromptsFilter(McpServerOptions options)
     {
-        options.Filters.Request.ListPromptsFilters.Add(next => async (context, cancellationToken) =>
+        options.Filters.Request.ListPromptsFilters.Add(next =>
         {
-            context.Items[AuthorizationFilterInvokedKey] = true;
+            var promptCollection = options.PromptCollection;
+            return async (context, cancellationToken) =>
+            {
+                context.Items[AuthorizationFilterInvokedKey] = true;
 
-            var result = await next(context, cancellationToken);
-            await FilterAuthorizedItemsAsync(
-                result.Prompts, static prompt => prompt.McpServerPrompt,
-                context.User, context.Services, context);
-            return result;
+                var result = await next(context, cancellationToken);
+                await FilterAuthorizedItemsAsync(
+                    result.Prompts, prompt => promptCollection is not null && promptCollection.TryGetPrimitive(prompt.Name, out var serverPrompt) ? serverPrompt : null,
+                    context.User, context.Services, context);
+                return result;
+            };
         });
     }
 
     private static void CheckListPromptsFilter(McpServerOptions options)
     {
-        options.Filters.Request.ListPromptsFilters.Add(next => async (context, cancellationToken) =>
+        options.Filters.Request.ListPromptsFilters.Add(next =>
         {
-            var result = await next(context, cancellationToken);
-
-            if (HasAuthorizationMetadata(result.Prompts.Select(static prompt => prompt.McpServerPrompt))
-                && !context.Items.ContainsKey(AuthorizationFilterInvokedKey))
+            var promptCollection = options.PromptCollection;
+            return async (context, cancellationToken) =>
             {
-                throw new InvalidOperationException("Authorization filter was not invoked for prompts/list operation, but authorization metadata was found on the prompts. Ensure that AddAuthorizationFilters() is called on the IMcpServerBuilder to configure authorization filters.");
-            }
+                var result = await next(context, cancellationToken);
 
-            return result;
+                if (HasAuthorizationMetadata(result.Prompts.Select(prompt => promptCollection is not null && promptCollection.TryGetPrimitive(prompt.Name, out var serverPrompt) ? serverPrompt : null))
+                    && !context.Items.ContainsKey(AuthorizationFilterInvokedKey))
+                {
+                    throw new InvalidOperationException("Authorization filter was not invoked for prompts/list operation, but authorization metadata was found on the prompts. Ensure that AddAuthorizationFilters() is called on the IMcpServerBuilder to configure authorization filters.");
+                }
+
+                return result;
+            };
         });
     }
 

src/ModelContextProtocol.Core/Protocol/Prompt.cs

@@ -1,7 +1,6 @@
 using System.Diagnostics;
 using System.Text.Json.Nodes;
 using System.Text.Json.Serialization;
-using ModelContextProtocol.Server;
 
 namespace ModelContextProtocol.Protocol;
 
@@ -72,12 +71,6 @@ public sealed class Prompt : IBaseMetadata
     [JsonPropertyName("_meta")]
     public JsonObject? Meta { get; set; }
 
-    /// <summary>
-    /// Gets or sets the callable server prompt corresponding to this metadata if any.
-    /// </summary>
-    [JsonIgnore]
-    public McpServerPrompt? McpServerPrompt { get; set; }
-
     [DebuggerBrowsable(DebuggerBrowsableState.Never)]
     private string DebuggerDisplay
     {

src/ModelContextProtocol.Core/Protocol/Resource.cs

@@ -2,7 +2,6 @@ using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Text.Json.Nodes;
 using System.Text.Json.Serialization;
-using ModelContextProtocol.Server;
 
 namespace ModelContextProtocol.Protocol;
 
@@ -101,10 +100,4 @@ public sealed class Resource : IBaseMetadata
     /// </remarks>
     [JsonPropertyName("_meta")]
     public JsonObject? Meta { get; set; }
-
-    /// <summary>
-    /// Gets or sets the callable server resource corresponding to this metadata if any.
-    /// </summary>
-    [JsonIgnore]
-    public McpServerResource? McpServerResource { get; set; }
 }

src/ModelContextProtocol.Core/Protocol/ResourceTemplate.cs

@@ -1,6 +1,5 @@
 using System.Text.Json.Nodes;
 using System.Text.Json.Serialization;
-using ModelContextProtocol.Server;
 
 namespace ModelContextProtocol.Protocol;
 
@@ -94,12 +93,6 @@ public sealed class ResourceTemplate : IBaseMetadata
     [JsonIgnore]
     public bool IsTemplated => UriTemplate.Contains('{');
 
-    /// <summary>
-    /// Gets or sets the callable server resource corresponding to this metadata, if any.
-    /// </summary>
-    [JsonIgnore]
-    public McpServerResource? McpServerResource { get; set; }
-
     /// <summary>Converts the <see cref="ResourceTemplate"/> into a <see cref="Resource"/>.</summary>
     /// <returns>A <see cref="Resource"/> if <see cref="IsTemplated"/> is <see langword="false"/>; otherwise, <see langword="null"/>.</returns>
     public Resource? AsResource()
@@ -119,7 +112,6 @@ public sealed class ResourceTemplate : IBaseMetadata
             Annotations = Annotations,
             Icons = Icons,
             Meta = Meta,
-            McpServerResource = McpServerResource,
         };
     }
 }

src/ModelContextProtocol.Core/Protocol/Tool.cs

@@ -1,4 +1,3 @@
-using ModelContextProtocol.Server;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Text.Json;
@@ -158,12 +157,6 @@ public sealed class Tool : IBaseMetadata
     [JsonPropertyName("_meta")]
     public JsonObject? Meta { get; set; }
 
-    /// <summary>
-    /// Gets or sets the callable server tool corresponding to this metadata if any.
-    /// </summary>
-    [JsonIgnore]
-    public McpServerTool? McpServerTool { get; set; }
-
     [DebuggerBrowsable(DebuggerBrowsableState.Never)]
     private string DebuggerDisplay
     {

src/ModelContextProtocol.Core/Server/AIFunctionMcpServerPrompt.cs

@@ -182,7 +182,6 @@ internal sealed class AIFunctionMcpServerPrompt : McpServerPrompt
     {
         AIFunction = function;
         ProtocolPrompt = prompt;
-        ProtocolPrompt.McpServerPrompt = this;
         _metadata = metadata;
     }
 

src/ModelContextProtocol.Core/Server/AIFunctionMcpServerResource.cs

@@ -294,7 +294,6 @@ internal sealed class AIFunctionMcpServerResource : McpServerResource
     {
         AIFunction = function;
         ProtocolResourceTemplate = resourceTemplate;
-        ProtocolResourceTemplate.McpServerResource = this;
         ProtocolResource = resourceTemplate.AsResource();
         _metadata = metadata;
 

src/ModelContextProtocol.Core/Server/AIFunctionMcpServerTool.cs

@@ -234,7 +234,6 @@ internal sealed partial class AIFunctionMcpServerTool : McpServerTool
 
         AIFunction = function;
         ProtocolTool = tool;
-        ProtocolTool.McpServerTool = this;
 
         _structuredOutputRequiresWrapping = structuredOutputRequiresWrapping;
         _metadata = metadata;

tests/ModelContextProtocol.AspNetCore.Tests/AuthorizeAttributeTests.cs

@@ -398,6 +398,105 @@ public class AuthorizeAttributeTests(ITestOutputHelper testOutputHelper) : Kestr
             log.Exception.Message.Contains("Ensure that AddAuthorizationFilters() is called"));
     }
 
+    [Fact]
+    public async Task ListTools_WithHandlerAndNullCollection_AllToolsVisible()
+    {
+        // When ToolCollection is null (custom handler only), the auth filter can't look up
+        // primitives in the collection and should not filter any tools.
+        await using var app = await StartServerWithAuth(builder =>
+            builder.WithListToolsHandler(static (_, _) => ValueTask.FromResult(new ListToolsResult
+            {
+                Tools = [new Tool { Name = "custom_tool" }]
+            })));
+
+        var client = await ConnectAsync();
+        var tools = await client.ListToolsAsync(cancellationToken: TestContext.Current.CancellationToken);
+
+        // Tool from custom handler (not in ToolCollection) should be visible even to anonymous users
+        Assert.Single(tools);
+        Assert.Equal("custom_tool", tools[0].Name);
+    }
+
+    [Fact]
+    public async Task ListTools_WithMixedCollectionAndHandler_HandlerToolsNotFiltered()
+    {
+        // Tools in the ToolCollection are filtered based on auth metadata.
+        // Tools returned only from a custom handler (not in ToolCollection) are not filtered.
+        await using var app = await StartServerWithAuth(builder =>
+        {
+            builder.WithTools<AuthorizationTestTools>();
+            builder.WithListToolsHandler(static (_, _) => ValueTask.FromResult(new ListToolsResult
+            {
+                Tools = [new Tool { Name = "handler_tool" }]
+            }));
+        });
+
+        var client = await ConnectAsync();
+        var tools = await client.ListToolsAsync(cancellationToken: TestContext.Current.CancellationToken);
+
+        // Anonymous user: anonymous_tool from collection + handler_tool (not in collection, so not filtered)
+        Assert.Equal(2, tools.Count);
+        var toolNames = tools.Select(t => t.Name).OrderBy(n => n).ToList();
+        Assert.Equal(["anonymous_tool", "handler_tool"], toolNames);
+    }
+
+    [Fact]
+    public async Task ListPrompts_WithHandlerAndNullCollection_AllPromptsVisible()
+    {
+        // When PromptCollection is null (custom handler only), the auth filter can't look up
+        // primitives in the collection and should not filter any prompts.
+        await using var app = await StartServerWithAuth(builder =>
+            builder.WithListPromptsHandler(static (_, _) => ValueTask.FromResult(new ListPromptsResult
+            {
+                Prompts = [new Prompt { Name = "custom_prompt" }]
+            })));
+
+        var client = await ConnectAsync();
+        var prompts = await client.ListPromptsAsync(cancellationToken: TestContext.Current.CancellationToken);
+
+        // Prompt from custom handler (not in PromptCollection) should be visible even to anonymous users
+        Assert.Single(prompts);
+        Assert.Equal("custom_prompt", prompts[0].Name);
+    }
+
+    [Fact]
+    public async Task ListResources_WithHandlerAndNullCollection_AllResourcesVisible()
+    {
+        // When ResourceCollection is null (custom handler only), the auth filter can't look up
+        // primitives in the collection and should not filter any resources.
+        await using var app = await StartServerWithAuth(builder =>
+            builder.WithListResourcesHandler(static (_, _) => ValueTask.FromResult(new ListResourcesResult
+            {
+                Resources = [new Resource { Name = "custom_resource", Uri = "resource://custom" }]
+            })));
+
+        var client = await ConnectAsync();
+        var resources = await client.ListResourcesAsync(cancellationToken: TestContext.Current.CancellationToken);
+
+        // Resource from custom handler (not in ResourceCollection) should be visible even to anonymous users
+        Assert.Single(resources);
+        Assert.Equal("resource://custom", resources[0].Uri);
+    }
+
+    [Fact]
+    public async Task ListResourceTemplates_WithHandlerAndNullCollection_AllResourceTemplatesVisible()
+    {
+        // When ResourceCollection is null (custom handler only), the auth filter can't look up
+        // primitives in the collection and should not filter any resource templates.
+        await using var app = await StartServerWithAuth(builder =>
+            builder.WithListResourceTemplatesHandler(static (_, _) => ValueTask.FromResult(new ListResourceTemplatesResult
+            {
+                ResourceTemplates = [new ResourceTemplate { Name = "custom_template", UriTemplate = "resource://custom/{id}" }]
+            })));
+
+        var client = await ConnectAsync();
+        var templates = await client.ListResourceTemplatesAsync(cancellationToken: TestContext.Current.CancellationToken);
+
+        // Template from custom handler (not in ResourceCollection) should be visible even to anonymous users
+        Assert.Single(templates);
+        Assert.Equal("resource://custom/{id}", templates[0].UriTemplate);
+    }
+
     private async Task<WebApplication> StartServerWithAuth(Action<IMcpServerBuilder> configure, string? userName = null, params string[] roles)
     {
         var mcpServerBuilder = Builder.Services.AddMcpServer().WithHttpTransport().AddAuthorizationFilters();