Fix URI template derivation and lookup

samples/AspNetCoreSseServer/Program.cs

@@ -2,12 +2,14 @@
 using OpenTelemetry.Metrics;
 using OpenTelemetry.Trace;
 using TestServerWithHosting.Tools;
+using TestServerWithHosting.Resources;
 
 var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddMcpServer()
     .WithHttpTransport()
     .WithTools<EchoTool>()
-    .WithTools<SampleLlmTool>();
+    .WithTools<SampleLlmTool>()
+    .WithResources<SimpleResourceType>();
 
 builder.Services.AddOpenTelemetry()
     .WithTracing(b => b.AddSource("*")

samples/AspNetCoreSseServer/Resources/SimpleResourceType.cs

@@ -0,0 +1,12 @@
+using ModelContextProtocol.Protocol;
+using ModelContextProtocol.Server;
+using System.ComponentModel;
+
+namespace TestServerWithHosting.Resources;
+
+[McpServerResourceType]
+public class SimpleResourceType
+{
+    [McpServerResource, Description("A direct text resource")]
+    public static string DirectTextResource() => "This is a direct resource";
+}

src/ModelContextProtocol.Core/Server/AIFunctionMcpServerResource.cs

@@ -264,7 +264,7 @@ private static AIFunctionFactoryOptions CreateAIFunctionFactoryOptions(
             Name = name,
             Title = options?.Title,
             Description = options?.Description,
-            MimeType = options?.MimeType,
+            MimeType = options?.MimeType ?? "application/octet-stream",
         };
 
         return new AIFunctionMcpServerResource(function, resource);
@@ -295,7 +295,7 @@ private static string DeriveUriTemplate(string name, AIFunction function)
     {
         StringBuilder template = new();
 
-        template.Append("resource://").Append(Uri.EscapeDataString(name));
+        template.Append("resource:///").Append(Uri.EscapeDataString(name));
 
         if (function.JsonSchema.TryGetProperty("properties", out JsonElement properties))
         {

tests/ModelContextProtocol.Tests/Configuration/McpServerBuilderExtensionsResourcesTests.cs

@@ -220,7 +220,7 @@ public async Task Throws_When_Resource_Fails()
         await using IMcpClient client = await CreateMcpClientForServer();
 
         await Assert.ThrowsAsync<McpException>(async () => await client.ReadResourceAsync(
-            $"resource://{nameof(SimpleResources.ThrowsException)}",
+            $"resource:///{nameof(SimpleResources.ThrowsException)}",
             cancellationToken: TestContext.Current.CancellationToken));
     }
 
@@ -230,7 +230,7 @@ public async Task Throws_Exception_On_Unknown_Resource()
         await using IMcpClient client = await CreateMcpClientForServer();
 
         var e = await Assert.ThrowsAsync<McpException>(async () => await client.ReadResourceAsync(
-            "test://NotRegisteredResource",
+            "test:///NotRegisteredResource",
             cancellationToken: TestContext.Current.CancellationToken));
 
         Assert.Contains("Resource not found", e.Message);
@@ -268,8 +268,8 @@ public void Register_Resources_From_Current_Assembly()
         sc.AddMcpServer().WithResourcesFromAssembly();
         IServiceProvider services = sc.BuildServiceProvider();
 
-        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResource?.Uri == $"resource://{nameof(SimpleResources.SomeNeatDirectResource)}");
-        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResourceTemplate?.UriTemplate == $"resource://{nameof(SimpleResources.SomeNeatTemplatedResource)}{{?name}}");
+        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResource?.Uri == $"resource:///{nameof(SimpleResources.SomeNeatDirectResource)}");
+        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResourceTemplate?.UriTemplate == $"resource:///{nameof(SimpleResources.SomeNeatTemplatedResource)}{{?name}}");
     }
 
     [Fact]
@@ -279,13 +279,13 @@ public void Register_Resources_From_Multiple_Sources()
         sc.AddMcpServer()
             .WithResources<SimpleResources>()
             .WithResources<MoreResources>()
-            .WithResources([McpServerResource.Create(() => "42", new() { UriTemplate = "myResources://Returns42/{something}" })]);
+            .WithResources([McpServerResource.Create(() => "42", new() { UriTemplate = "myResources:///returns42/{something}" })]);
         IServiceProvider services = sc.BuildServiceProvider();
 
-        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResource?.Uri == $"resource://{nameof(SimpleResources.SomeNeatDirectResource)}");
-        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResourceTemplate?.UriTemplate == $"resource://{nameof(SimpleResources.SomeNeatTemplatedResource)}{{?name}}");
-        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResourceTemplate?.UriTemplate == $"resource://{nameof(MoreResources.AnotherNeatDirectResource)}");
-        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResourceTemplate.UriTemplate == "myResources://Returns42/{something}");
+        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResource?.Uri == $"resource:///{nameof(SimpleResources.SomeNeatDirectResource)}");
+        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResourceTemplate?.UriTemplate == $"resource:///{nameof(SimpleResources.SomeNeatTemplatedResource)}{{?name}}");
+        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResourceTemplate?.UriTemplate == $"resource:///{nameof(MoreResources.AnotherNeatDirectResource)}");
+        Assert.Contains(services.GetServices<McpServerResource>(), t => t.ProtocolResourceTemplate.UriTemplate == "myResources:///returns42/{something}");
     }
 
     [McpServerResourceType]