Change ProtectedResourceMetadata URI properties to strings and build resource strings directly

samples/ProtectedMcpServer/Program.cs

@@ -56,8 +56,8 @@
 {
     options.ResourceMetadata = new()
     {
-        ResourceDocumentation = new Uri("https://docs.example.com/api/weather"),
-        AuthorizationServers = { new Uri(inMemoryOAuthServerUrl) },
+        ResourceDocumentation = "https://docs.example.com/api/weather",
+        AuthorizationServers = { inMemoryOAuthServerUrl },
         ScopesSupported = ["mcp:tools"],
     };
 });

src/ModelContextProtocol.AspNetCore/Authentication/McpAuthenticationHandler.cs

@@ -165,7 +165,7 @@ private async Task<bool> HandleResourceMetadataRequestAsync(Uri? derivedResource
             throw new InvalidOperationException("ResourceMetadata has not been configured. Please set McpAuthenticationOptions.ResourceMetadata or ensure context.ResourceMetadata is set inside McpAuthenticationOptions.Events.OnResourceMetadataRequest.");
         }
 
-        resourceMetadata.Resource ??= derivedResourceUri;
+        resourceMetadata.Resource ??= derivedResourceUri?.ToString();
 
         if (resourceMetadata.Resource is null)
         {

src/ModelContextProtocol.Core/Authentication/ClientOAuthProvider.cs

@@ -154,7 +154,7 @@ internal override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage r
         // Try to refresh the access token if it is invalid and we have a refresh token.
         if (_authServerMetadata is not null && tokens?.RefreshToken is { Length: > 0 } refreshToken)
         {
-            var accessToken = await RefreshTokensAsync(refreshToken, resourceUri, _authServerMetadata, cancellationToken).ConfigureAwait(false);
+            var accessToken = await RefreshTokensAsync(refreshToken, resourceUri.ToString(), _authServerMetadata, cancellationToken).ConfigureAwait(false);
             return (accessToken, true);
         }
 
@@ -243,15 +243,26 @@ private async Task<string> GetAccessTokenAsync(HttpResponseMessage response, boo
             ThrowFailedToHandleUnauthorizedResponse("No authorization servers found in authentication challenge");
         }
 
+        // Convert string URIs to Uri objects for the selector
+        List<Uri> authServerUris = [];
+        foreach (var serverUriString in availableAuthorizationServers)
+        {
+            if (!Uri.TryCreate(serverUriString, UriKind.Absolute, out var serverUri))
+            {
+                ThrowFailedToHandleUnauthorizedResponse($"Invalid authorization server URI: '{serverUriString}'. Available servers: {string.Join(", ", availableAuthorizationServers)}");
+            }
+            authServerUris.Add(serverUri);
+        }
+
         // Select authorization server using configured strategy
-        var selectedAuthServer = _authServerSelector(availableAuthorizationServers);
+        var selectedAuthServer = _authServerSelector(authServerUris);
 
         if (selectedAuthServer is null)
         {
             ThrowFailedToHandleUnauthorizedResponse($"Authorization server selection returned null. Available servers: {string.Join(", ", availableAuthorizationServers)}");
         }
 
-        if (!availableAuthorizationServers.Contains(selectedAuthServer))
+        if (!authServerUris.Contains(selectedAuthServer))
         {
             ThrowFailedToHandleUnauthorizedResponse($"Authorization server selector returned a server not in the available list: {selectedAuthServer}. Available servers: {string.Join(", ", availableAuthorizationServers)}");
         }
@@ -387,13 +398,13 @@ private static IEnumerable<Uri> GetWellKnownAuthorizationServerMetadataUris(Uri
         }
     }
 
-    private async Task<string?> RefreshTokensAsync(string refreshToken, Uri resourceUri, AuthorizationServerMetadata authServerMetadata, CancellationToken cancellationToken)
+    private async Task<string?> RefreshTokensAsync(string refreshToken, string resourceUri, AuthorizationServerMetadata authServerMetadata, CancellationToken cancellationToken)
     {
         Dictionary<string, string> formFields = new()
         {
             ["grant_type"] = "refresh_token",
             ["refresh_token"] = refreshToken,
-            ["resource"] = resourceUri.ToString(),
+            ["resource"] = resourceUri,
         };
 
         using var request = CreateTokenRequest(authServerMetadata.TokenEndpoint, formFields);
@@ -443,7 +454,7 @@ private Uri BuildAuthorizationUrl(
             ["response_type"] = "code",
             ["code_challenge"] = codeChallenge,
             ["code_challenge_method"] = "S256",
-            ["resource"] = resourceUri.ToString(),
+            ["resource"] = resourceUri,
         };
 
         var scope = GetScopeParameter(protectedResourceMetadata);
@@ -487,7 +498,7 @@ private async Task<string> ExchangeCodeForTokenAsync(
             ["code"] = authorizationCode,
             ["redirect_uri"] = _redirectUri.ToString(),
             ["code_verifier"] = codeVerifier,
-            ["resource"] = resourceUri.ToString(),
+            ["resource"] = resourceUri,
         };
 
         using var request = CreateTokenRequest(authServerMetadata.TokenEndpoint, formFields);
@@ -659,7 +670,7 @@ private async Task PerformDynamicClientRegistrationAsync(
         }
     }
 
-    private static Uri GetRequiredResourceUri(ProtectedResourceMetadata protectedResourceMetadata)
+    private static string GetRequiredResourceUri(ProtectedResourceMetadata protectedResourceMetadata)
     {
         if (protectedResourceMetadata.Resource is null)
         {
@@ -732,6 +743,27 @@ private static string NormalizeUri(Uri uri)
         return builder.ToString();
     }
 
+    /// <summary>
+    /// Normalizes a URI string for consistent comparison.
+    /// </summary>
+    /// <param name="uriString">The URI string to normalize.</param>
+    /// <returns>
+    /// A normalized string representation of the URI. If the string is a valid absolute URI,
+    /// it is parsed and normalized (scheme, host, port, and path without trailing slash).
+    /// If the string is not a valid absolute URI, only the trailing slash is removed.
+    /// </returns>
+    private static string NormalizeUri(string uriString)
+    {
+        // Parse the string as a URI to normalize it
+        if (!Uri.TryCreate(uriString, UriKind.Absolute, out var uri))
+        {
+            // If it's not a valid URI, return the string with trailing slash removed
+            return uriString.TrimEnd('/');
+        }
+
+        return NormalizeUri(uri);
+    }
+
     /// <summary>
     /// Responds to a 401 challenge by parsing the WWW-Authenticate header, fetching the resource metadata,
     /// verifying the resource match, and returning the metadata if valid.

src/ModelContextProtocol.Core/Authentication/ProtectedResourceMetadata.cs

@@ -20,7 +20,7 @@ public sealed class ProtectedResourceMetadata
     /// <b>Resource</b> must be explicitly set. Automatic inference only works with the default endpoint pattern.
     /// </remarks>
     [JsonPropertyName("resource")]
-    public Uri? Resource { get; set; }
+    public string? Resource { get; set; }
 
     /// <summary>
     /// Gets or sets the list of authorization server URIs.
@@ -33,7 +33,7 @@ public sealed class ProtectedResourceMetadata
     /// OPTIONAL.
     /// </remarks>
     [JsonPropertyName("authorization_servers")]
-    public List<Uri> AuthorizationServers { get; set; } = [];
+    public List<string> AuthorizationServers { get; set; } = [];
 
     /// <summary>
     /// Gets or sets the supported bearer token methods.
@@ -69,7 +69,7 @@ public sealed class ProtectedResourceMetadata
     /// that the resource server uses to sign resource responses. This URL MUST use the HTTPS scheme.
     /// </remarks>
     [JsonPropertyName("jwks_uri")]
-    public Uri? JwksUri { get; set; }
+    public string? JwksUri { get; set; }
 
     /// <summary>
     /// Gets or sets the list of the JWS signing algorithms supported by the protected resource for signing resource responses.
@@ -105,7 +105,7 @@ public sealed class ProtectedResourceMetadata
     /// OPTIONAL.
     /// </remarks>
     [JsonPropertyName("resource_documentation")]
-    public Uri? ResourceDocumentation { get; set; }
+    public string? ResourceDocumentation { get; set; }
 
     /// <summary>
     /// Gets or sets the URL of a page containing human-readable information about the protected resource's requirements.
@@ -117,7 +117,7 @@ public sealed class ProtectedResourceMetadata
     /// OPTIONAL.
     /// </remarks>
     [JsonPropertyName("resource_policy_uri")]
-    public Uri? ResourcePolicyUri { get; set; }
+    public string? ResourcePolicyUri { get; set; }
 
     /// <summary>
     /// Gets or sets the URL of a page containing human-readable information about the protected resource's terms of service.
@@ -126,7 +126,7 @@ public sealed class ProtectedResourceMetadata
     /// OPTIONAL. The value of this field MAY be internationalized.
     /// </remarks>
     [JsonPropertyName("resource_tos_uri")]
-    public Uri? ResourceTosUri { get; set; }
+    public string? ResourceTosUri { get; set; }
 
     /// <summary>
     /// Gets or sets a value indicating whether there is protected resource support for mutual-TLS client certificate-bound access tokens.
@@ -201,7 +201,7 @@ public ProtectedResourceMetadata Clone(Uri? derivedResourceUri = null)
     {
         return new ProtectedResourceMetadata
         {
-            Resource = Resource ?? derivedResourceUri,
+            Resource = Resource ?? derivedResourceUri?.ToString(),
             AuthorizationServers = [.. AuthorizationServers],
             BearerMethodsSupported = [.. BearerMethodsSupported],
             ScopesSupported = [.. ScopesSupported],

tests/ModelContextProtocol.AspNetCore.Tests/OAuth/AuthEventTests.cs

@@ -25,8 +25,8 @@ public AuthEventTests(ITestOutputHelper outputHelper)
                 // Dynamically provide the resource metadata
                 context.ResourceMetadata = new ProtectedResourceMetadata
                 {
-                    Resource = new Uri(McpServerUrl),
-                    AuthorizationServers = { new Uri(OAuthServerUrl) },
+                    Resource = McpServerUrl,
+                    AuthorizationServers = { OAuthServerUrl },
                     ScopesSupported = ["mcp:tools"],
                 };
                 await Task.CompletedTask;
@@ -124,8 +124,8 @@ public async Task ResourceMetadataEndpoint_ReturnsCorrectMetadata_FromEvent()
         );
 
         Assert.NotNull(metadata);
-        Assert.Equal(new Uri(McpServerUrl), metadata.Resource);
-        Assert.Contains(new Uri(OAuthServerUrl), metadata.AuthorizationServers);
+        Assert.Equal(McpServerUrl, metadata.Resource);
+        Assert.Contains(OAuthServerUrl, metadata.AuthorizationServers);
         Assert.Contains("mcp:tools", metadata.ScopesSupported);
     }
 
@@ -140,8 +140,8 @@ public async Task ResourceMetadataEndpoint_CanModifyExistingMetadata_InEvent()
                 // Set initial metadata
                 options.ResourceMetadata = new ProtectedResourceMetadata
                 {
-                    Resource = new Uri(McpServerUrl),
-                    AuthorizationServers = { new Uri(OAuthServerUrl) },
+                    Resource = McpServerUrl,
+                    AuthorizationServers = { OAuthServerUrl },
                     ScopesSupported = ["mcp:basic"],
                 };
 
@@ -175,8 +175,8 @@ public async Task ResourceMetadataEndpoint_CanModifyExistingMetadata_InEvent()
         );
 
         Assert.NotNull(metadata);
-        Assert.Equal(new Uri(McpServerUrl), metadata.Resource);
-        Assert.Contains(new Uri(OAuthServerUrl), metadata.AuthorizationServers);
+        Assert.Equal(McpServerUrl, metadata.Resource);
+        Assert.Contains(OAuthServerUrl, metadata.AuthorizationServers);
         Assert.Contains("mcp:basic", metadata.ScopesSupported);
         Assert.Contains("mcp:tools", metadata.ScopesSupported);
         Assert.Equal("Dynamic Test Resource", metadata.ResourceName);

tests/ModelContextProtocol.AspNetCore.Tests/OAuth/AuthTests.cs

@@ -9,6 +9,7 @@
 using ModelContextProtocol.Client;
 using ModelContextProtocol.Server;
 using System.Net;
+using System.Net.Http.Json;
 using System.Security.Claims;
 using Xunit.Sdk;
 
@@ -506,7 +507,7 @@ public async Task AuthorizationFails_WhenResourceMetadataPortDiffers()
     {
         Builder.Services.Configure<McpAuthenticationOptions>(McpAuthenticationDefaults.AuthenticationScheme, options =>
         {
-            options.ResourceMetadata!.Resource = new Uri("http://localhost:5999");
+            options.ResourceMetadata!.Resource = "http://localhost:5999";
         });
 
         await using var app = await StartMcpServerAsync();
@@ -532,7 +533,7 @@ public async Task CanAuthenticate_WithAuthorizationServerPathInsertionMetadata()
     {
         Builder.Services.Configure<McpAuthenticationOptions>(McpAuthenticationDefaults.AuthenticationScheme, options =>
         {
-            options.ResourceMetadata!.AuthorizationServers = [new Uri($"{OAuthServerUrl}/tenant1")];
+            options.ResourceMetadata!.AuthorizationServers = [$"{OAuthServerUrl}/tenant1"];
         });
 
         await using var app = await StartMcpServerAsync();
@@ -565,7 +566,7 @@ public async Task CanAuthenticate_WithAuthorizationServerPathFallbacks()
 
         Builder.Services.Configure<McpAuthenticationOptions>(McpAuthenticationDefaults.AuthenticationScheme, options =>
         {
-            options.ResourceMetadata!.AuthorizationServers = [new Uri($"{OAuthServerUrl}{issuerPath}")];
+            options.ResourceMetadata!.AuthorizationServers = [$"{OAuthServerUrl}{issuerPath}"];
         });
 
         await using var app = await StartMcpServerAsync();
@@ -606,8 +607,8 @@ public async Task CanAuthenticate_WithResourceMetadataPathFallbacks()
 
         var metadata = new ProtectedResourceMetadata
         {
-            Resource = new Uri($"{McpServerUrl}{resourcePath}"),
-            AuthorizationServers = { new Uri(OAuthServerUrl) },
+            Resource = $"{McpServerUrl}{resourcePath}",
+            AuthorizationServers = { OAuthServerUrl },
         };
 
         app.Use(async (context, next) =>
@@ -678,8 +679,8 @@ public async Task CannotAuthenticate_WhenResourceMetadataResourceIsNonRootParent
         {
             options.ResourceMetadata = new ProtectedResourceMetadata
             {
-                Resource = new Uri($"{McpServerUrl}{configuredResourcePath}"),
-                AuthorizationServers = { new Uri(OAuthServerUrl) },
+                Resource = $"{McpServerUrl}{configuredResourcePath}",
+                AuthorizationServers = { OAuthServerUrl },
             };
         });
 
@@ -719,8 +720,8 @@ public async Task CannotAuthenticate_WhenWwwAuthenticateResourceMetadataIsRootPa
         {
             options.ResourceMetadata = new ProtectedResourceMetadata
             {
-                Resource = new Uri($"{McpServerUrl}"),
-                AuthorizationServers = { new Uri(OAuthServerUrl) },
+                Resource = McpServerUrl,
+                AuthorizationServers = { OAuthServerUrl },
             };
         });
 
@@ -750,4 +751,42 @@ await McpClient.CreateAsync(
 
         Assert.Contains("does not match", ex.Message);
     }
+
+    [Fact]
+    public async Task ResourceMetadata_DoesNotAddTrailingSlash()
+    {
+        // This test verifies that using string for Resource property avoids URI normalization
+        // that would add a trailing slash to URIs without paths
+        const string resourceWithoutTrailingSlash = "http://localhost:5000";
+
+        Builder.Services.Configure<McpAuthenticationOptions>(McpAuthenticationDefaults.AuthenticationScheme, options =>
+        {
+            options.ResourceMetadata = new ProtectedResourceMetadata
+            {
+                Resource = resourceWithoutTrailingSlash,
+                AuthorizationServers = { OAuthServerUrl },
+                ScopesSupported = ["mcp:tools"],
+            };
+        });
+
+        await using var app = await StartMcpServerAsync();
+
+        // Make a direct request to the resource metadata endpoint
+        using var response = await HttpClient.GetAsync(
+            "/.well-known/oauth-protected-resource",
+            TestContext.Current.CancellationToken
+        );
+
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+
+        var metadata = await response.Content.ReadFromJsonAsync<ProtectedResourceMetadata>(
+            McpJsonUtilities.DefaultOptions,
+            TestContext.Current.CancellationToken
+        );
+
+        Assert.NotNull(metadata);
+
+        // Verify that the Resource property does NOT have a trailing slash added
+        Assert.Equal(resourceWithoutTrailingSlash, metadata.Resource);
+    }
 }

tests/ModelContextProtocol.AspNetCore.Tests/OAuth/McpAuthenticationHandlerTests.cs

@@ -23,7 +23,7 @@ public async Task Challenge_WithRelativeResourceMetadataUri_SetsAbsoluteUrl()
         await using var app = await StartAuthenticationServerAsync(options =>
         {
             options.ResourceMetadataUri = new Uri(metadataPath, UriKind.Relative);
-            options.ResourceMetadata!.Resource = new Uri("http://localhost:5000/challenge");
+            options.ResourceMetadata!.Resource = "http://localhost:5000/challenge";
         });
 
         using var challengeResponse = await HttpClient.GetAsync(new Uri("/challenge", UriKind.Relative), HttpCompletionOption.ResponseHeadersRead, TestContext.Current.CancellationToken);
@@ -64,7 +64,7 @@ public async Task Challenge_WithAbsoluteResourceMetadataUri_SetsConfiguredUrl()
         await using var app = await StartAuthenticationServerAsync(options =>
         {
             options.ResourceMetadataUri = metadataUri;
-            options.ResourceMetadata!.Resource = new Uri("http://localhost:5000/challenge");
+            options.ResourceMetadata!.Resource = "http://localhost:5000/challenge";
         });
 
         using var challengeResponse = await HttpClient.GetAsync(new Uri("/challenge", UriKind.Relative), HttpCompletionOption.ResponseHeadersRead, TestContext.Current.CancellationToken);
@@ -137,7 +137,7 @@ public async Task MetadataRequest_DefaultEndpoint_SetsResourceFromSuffix()
             McpJsonUtilities.DefaultOptions,
             TestContext.Current.CancellationToken);
         Assert.NotNull(metadata);
-        Assert.Equal(new Uri("http://localhost:5000/resource/tools"), metadata!.Resource);
+        Assert.Equal("http://localhost:5000/resource/tools", metadata!.Resource);
     }
 
     [Fact]
@@ -153,7 +153,7 @@ public async Task MetadataRequest_DefaultEndpoint_WithPathBase_SetsResourceFromS
             McpJsonUtilities.DefaultOptions,
             TestContext.Current.CancellationToken);
         Assert.NotNull(metadata);
-        Assert.Equal(new Uri("http://localhost:5000/api/resource/tools"), metadata!.Resource);
+        Assert.Equal("http://localhost:5000/api/resource/tools", metadata!.Resource);
     }
 
     private async Task<WebApplication> StartAuthenticationServerAsync(Action<McpAuthenticationOptions>? configureOptions = null, PathString? pathBase = null)
@@ -169,7 +169,7 @@ private async Task<WebApplication> StartAuthenticationServerAsync(Action<McpAuth
         {
             options.ResourceMetadata = new()
             {
-                AuthorizationServers = [new Uri("https://localhost:7029")],
+                AuthorizationServers = ["https://localhost:7029"],
                 ScopesSupported = ["mcp:tools"],
             };
             configureOptions?.Invoke(options);