Fix case-sensitive tenant ID comparison and introduce StringComparisons helper

core/Azure.Mcp.Core/src/Areas/Subscription/Commands/SubscriptionListCommand.cs

@@ -7,6 +7,7 @@
 using Azure.ResourceManager.Resources;
 using Microsoft.Extensions.Logging;
 using Microsoft.Mcp.Core.Commands;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Core.Models.Command;
 
 namespace Azure.Mcp.Core.Areas.Subscription.Commands;
@@ -65,7 +66,7 @@ internal static List<SubscriptionInfo> MapToSubscriptionInfos(List<SubscriptionD
             s.DisplayName,
             s.State?.ToString(),
             s.TenantId?.ToString(),
-            hasDefault && s.SubscriptionId.Equals(defaultSubscriptionId, StringComparison.OrdinalIgnoreCase)
+            hasDefault && s.SubscriptionId.Equals(defaultSubscriptionId, StringComparisons.SubscriptionId)
         )).ToList();
 
         // Sort so the default subscription appears first

core/Azure.Mcp.Core/src/Services/Azure/ResourceGroup/ResourceGroupService.cs

@@ -4,6 +4,7 @@
 using Azure.Mcp.Core.Services.Azure.Subscription;
 using Azure.Mcp.Core.Services.Azure.Tenant;
 using Azure.ResourceManager.Resources;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Core.Models.Resource;
 using Microsoft.Mcp.Core.Models.ResourceGroup;
 using Microsoft.Mcp.Core.Options;
@@ -65,7 +66,7 @@ public async Task<List<ResourceGroupInfo>> GetResourceGroups(string subscription
         var cachedResults = await _cacheService.GetAsync<List<ResourceGroupInfo>>(CacheGroup, cacheKey, s_cacheDuration, cancellationToken);
         if (cachedResults != null)
         {
-            return cachedResults.FirstOrDefault(rg => rg.Name.Equals(resourceGroupName, StringComparison.OrdinalIgnoreCase));
+            return cachedResults.FirstOrDefault(rg => rg.Name.Equals(resourceGroupName, StringComparisons.ResourceGroup));
         }
 
         var rg = await GetResourceGroupResource(subscription, resourceGroupName, tenant, retryPolicy, cancellationToken);

core/Azure.Mcp.Core/src/Services/Azure/Subscription/SubscriptionService.cs

@@ -94,7 +94,7 @@ public bool IsSubscriptionId(string subscription, string? tenant = null)
     public async Task<string> GetSubscriptionIdByName(string subscriptionName, string? tenant = null, RetryPolicyOptions? retryPolicy = null, CancellationToken cancellationToken = default)
     {
         var subscriptions = await GetSubscriptions(tenant, retryPolicy, cancellationToken);
-        var subscription = subscriptions.FirstOrDefault(s => s.DisplayName.Equals(subscriptionName, StringComparison.OrdinalIgnoreCase)) ??
+        var subscription = subscriptions.FirstOrDefault(s => s.DisplayName.Equals(subscriptionName, StringComparisons.SubscriptionDisplayName)) ??
             throw new KeyNotFoundException($"Could not find subscription with name {subscriptionName}");
 
         return subscription.SubscriptionId;
@@ -103,7 +103,7 @@ public async Task<string> GetSubscriptionIdByName(string subscriptionName, strin
     public async Task<string> GetSubscriptionNameById(string subscriptionId, string? tenant = null, RetryPolicyOptions? retryPolicy = null, CancellationToken cancellationToken = default)
     {
         var subscriptions = await GetSubscriptions(tenant, retryPolicy, cancellationToken);
-        var subscription = subscriptions.FirstOrDefault(s => s.SubscriptionId.Equals(subscriptionId, StringComparison.OrdinalIgnoreCase)) ??
+        var subscription = subscriptions.FirstOrDefault(s => s.SubscriptionId.Equals(subscriptionId, StringComparisons.SubscriptionId)) ??
             throw new KeyNotFoundException($"Could not find subscription with ID {subscriptionId}");
 
         return subscription.DisplayName;

core/Azure.Mcp.Core/src/Services/Azure/Tenant/TenantService.cs

@@ -6,6 +6,7 @@
 using Azure.ResourceManager;
 using Azure.ResourceManager.Resources;
 using Microsoft.Extensions.Logging;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Core.Services.Azure.Authentication;
 using Microsoft.Mcp.Core.Services.Caching;
 
@@ -107,7 +108,7 @@ public async Task<string> GetTenantIdByName(string tenantName, CancellationToken
     public async Task<string> GetTenantNameById(string tenantId, CancellationToken cancellationToken)
     {
         var tenants = await GetTenants(cancellationToken);
-        var tenant = tenants.FirstOrDefault(t => t.Data.TenantId?.ToString().Equals(tenantId, StringComparison.OrdinalIgnoreCase) == true) ??
+        var tenant = tenants.FirstOrDefault(t => t.Data.TenantId?.ToString().Equals(tenantId, StringComparisons.TenantId) == true) ??
             throw new KeyNotFoundException($"Could not find tenant with ID {tenantId}");
 
         string? tenantName = tenant.Data.DisplayName ??

core/Microsoft.Mcp.Core/src/Helpers/StringComparisons.cs

@@ -0,0 +1,44 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Microsoft.Mcp.Core.Helpers;
+
+/// <summary>
+/// Centralizes the <see cref="StringComparison"/> values to use when comparing
+/// well-known string values, making the intended comparison semantics explicit
+/// at each call site.
+/// </summary>
+public static class StringComparisons
+{
+    /// <summary>
+    /// The comparison to use when comparing Azure tenant IDs. Tenant IDs are
+    /// GUIDs whose casing is not significant, so they are compared
+    /// case-insensitively.
+    /// </summary>
+    public static StringComparison TenantId => StringComparison.OrdinalIgnoreCase;
+
+    /// <summary>
+    /// The comparison to use when comparing Azure subscription IDs. Subscription
+    /// IDs are GUIDs whose casing is not significant, so they are compared
+    /// case-insensitively.
+    /// </summary>
+    public static StringComparison SubscriptionId => StringComparison.OrdinalIgnoreCase;
+
+    /// <summary>
+    /// The comparison to use when comparing Azure subscription display names,
+    /// which are matched case-insensitively.
+    /// </summary>
+    public static StringComparison SubscriptionDisplayName => StringComparison.OrdinalIgnoreCase;
+
+    /// <summary>
+    /// The comparison to use when comparing Azure resource group names, which
+    /// Azure Resource Manager treats case-insensitively.
+    /// </summary>
+    public static StringComparison ResourceGroup => StringComparison.OrdinalIgnoreCase;
+
+    /// <summary>
+    /// The comparison to use when matching an Azure resource by its name. Azure
+    /// resource names are matched case-insensitively for lookup purposes.
+    /// </summary>
+    public static StringComparison ResourceName => StringComparison.OrdinalIgnoreCase;
+}

core/Microsoft.Mcp.Core/src/Services/Azure/Authentication/HttpOnBehalfOfTokenCredentialProvider.cs

@@ -6,6 +6,7 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 using Microsoft.Identity.Web;
+using Microsoft.Mcp.Core.Helpers;
 
 namespace Microsoft.Mcp.Core.Services.Azure.Authentication;
 
@@ -33,7 +34,7 @@ public Task<TokenCredential> GetTokenCredentialAsync(string? tenantId, Cancellat
         if (tenantId is not null)
         {
             if (httpContext.User.FindFirst("tid")?.Value is string tidClaim
-                && tidClaim != tenantId)
+                && !string.Equals(tidClaim, tenantId, StringComparisons.TenantId))
             {
                 _logger.LogWarning(
                     "The requested token tenant '{GetTokenTenant}' does not match the tenant of the authenticated user '{TidClaim}'. Going to throw.",

tools/Azure.Mcp.Tools.AppLens/src/Services/AppLensService.cs

@@ -16,6 +16,7 @@
 using Microsoft.AspNetCore.SignalR.Client;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Core.Services.Azure.Authentication;
 
 namespace Azure.Mcp.Tools.AppLens.Services;
@@ -107,7 +108,7 @@ internal async Task<FindResourceIdResult> FindResourceAsync(
         if (!string.IsNullOrEmpty(resourceGroup))
         {
             var rgFiltered = filteredResults
-                .Where(r => r.ResourceGroup.Equals(resourceGroup, StringComparison.OrdinalIgnoreCase))
+                .Where(r => r.ResourceGroup.Equals(resourceGroup, StringComparisons.ResourceGroup))
                 .ToImmutableArray();
 
             if (rgFiltered.Length == 0)

tools/Azure.Mcp.Tools.AzureBackup/src/Services/AzureBackupService.cs

@@ -12,6 +12,7 @@
 using Azure.ResourceManager.RecoveryServicesBackup.Models;
 using Azure.ResourceManager.Resources;
 using Microsoft.Extensions.Logging;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Core.Options;
 
 using SdkBackupStatusResult = Azure.ResourceManager.RecoveryServicesBackup.Models.BackupStatusResult;
@@ -135,7 +136,7 @@ public async Task<List<BackupVaultInfo>> ListVaultsAsync(
         List<BackupVaultInfo> FilterByResourceGroup(List<BackupVaultInfo> vaults) =>
             string.IsNullOrEmpty(resourceGroup)
                 ? vaults
-                : vaults.Where(v => string.Equals(v.ResourceGroup, resourceGroup, StringComparison.OrdinalIgnoreCase)).ToList();
+                : vaults.Where(v => string.Equals(v.ResourceGroup, resourceGroup, StringComparisons.ResourceGroup)).ToList();
 
         if (VaultTypeResolver.IsRsv(vaultType))
         {
@@ -658,7 +659,7 @@ public async Task<List<UnprotectedResourceInfo>> FindUnprotectedResourcesAsync(
 
                 // Apply optional resource group filter
                 if (!string.IsNullOrEmpty(resourceGroup) &&
-                    !string.Equals(resource.Id?.ResourceGroupName, resourceGroup, StringComparison.OrdinalIgnoreCase))
+                    !string.Equals(resource.Id?.ResourceGroupName, resourceGroup, StringComparisons.ResourceGroup))
                 {
                     continue;
                 }

tools/Azure.Mcp.Tools.AzureIsv/tests/Azure.Mcp.Tools.AzureIsv.Tests/AzureIsvCommandTests.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT License.
 
 using System.Text.Json;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Tests;
 using Microsoft.Mcp.Tests.Client;
 using Microsoft.Mcp.Tests.Client.Helpers;
@@ -17,7 +18,7 @@ public class AzureIsvCommandTests(ITestOutputHelper output, TestProxyFixture fix
     public async Task Should_list_datadog_monitored_resources()
     {
         // Skipping test if Tenant is not 'Customer LED Tenant'
-        if (Settings.TenantId != "888d76fa-54b2-4ced-8ee5-aac1585adee7" && Settings.TestMode != TestMode.Playback)
+        if (!string.Equals(Settings.TenantId, "888d76fa-54b2-4ced-8ee5-aac1585adee7", StringComparisons.TenantId) && Settings.TestMode != TestMode.Playback)
         {
             Assert.Skip("Test skipped because Tenant is not 'Customer LED Tenant'.");
         }

tools/Azure.Mcp.Tools.Compute/src/Commands/Disk/DiskUpdateCommand.cs

@@ -8,6 +8,7 @@
 using Azure.Mcp.Tools.Compute.Services;
 using Microsoft.Mcp.Core.Commands;
 using Microsoft.Mcp.Core.Extensions;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Core.Models.Command;
 using Microsoft.Mcp.Core.Models.Option;
 
@@ -132,7 +133,7 @@ public override async Task<CommandResponse> ExecuteAsync(CommandContext context,
                     cancellationToken);
 
                 var matchingDisks = disks
-                    .Where(d => string.Equals(d.Name, options.Disk, StringComparison.OrdinalIgnoreCase))
+                    .Where(d => string.Equals(d.Name, options.Disk, StringComparisons.ResourceName))
                     .ToList();
 
                 if (matchingDisks.Count == 0)

tools/Azure.Mcp.Tools.Cosmos/src/Services/CosmosService.cs

@@ -78,7 +78,7 @@ private async Task<CosmosDBAccountResource> GetCosmosAccountAsync(
         await foreach (var account in subscriptionResource.GetCosmosDBAccountsAsync(cancellationToken))
         {
             // Cosmos DB account names are case-insensitive in Azure, so compare accordingly.
-            if (account.Data.Name.Equals(accountName, StringComparison.OrdinalIgnoreCase))
+            if (account.Data.Name.Equals(accountName, StringComparisons.ResourceName))
             {
                 return account;
             }

tools/Azure.Mcp.Tools.EventGrid/src/Services/EventGridService.cs

@@ -8,6 +8,7 @@
 using Azure.ResourceManager.EventGrid;
 using Azure.ResourceManager.EventGrid.Models;
 using Azure.ResourceManager.Resources;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Core.Options;
 
 namespace Azure.Mcp.Tools.EventGrid.Services;
@@ -374,7 +375,7 @@ private async Task GetSubscriptionsFromAllTopics(
 
             await foreach (var topic in resourceGroupResource.Value.GetEventGridTopics().GetAllAsync(cancellationToken: cancellationToken))
             {
-                if (topic.Data.Name.Equals(topicName, StringComparison.OrdinalIgnoreCase))
+                if (topic.Data.Name.Equals(topicName, StringComparisons.ResourceName))
                 {
                     return topic;
                 }
@@ -385,7 +386,7 @@ private async Task GetSubscriptionsFromAllTopics(
             // Search in all resource groups
             await foreach (var topic in subscriptionResource.GetEventGridTopicsAsync(cancellationToken: cancellationToken))
             {
-                if (topic.Data.Name.Equals(topicName, StringComparison.OrdinalIgnoreCase))
+                if (topic.Data.Name.Equals(topicName, StringComparisons.ResourceName))
                 {
                     return topic;
                 }
@@ -408,7 +409,7 @@ private async Task GetSubscriptionsFromAllTopics(
 
             await foreach (var systemTopic in resourceGroupResource.Value.GetSystemTopics().GetAllAsync(cancellationToken: cancellationToken))
             {
-                if (systemTopic.Data.Name.Equals(topicName, StringComparison.OrdinalIgnoreCase))
+                if (systemTopic.Data.Name.Equals(topicName, StringComparisons.ResourceName))
                 {
                     return systemTopic;
                 }
@@ -419,7 +420,7 @@ private async Task GetSubscriptionsFromAllTopics(
             // Search in all resource groups
             await foreach (var systemTopic in subscriptionResource.GetSystemTopicsAsync(cancellationToken: cancellationToken))
             {
-                if (systemTopic.Data.Name.Equals(topicName, StringComparison.OrdinalIgnoreCase))
+                if (systemTopic.Data.Name.Equals(topicName, StringComparisons.ResourceName))
                 {
                     return systemTopic;
                 }

tools/Azure.Mcp.Tools.FileShares/src/Services/FileSharesService.cs

@@ -4,6 +4,7 @@
 using System.Net;
 using Azure.ResourceManager.FileShares;
 using Azure.ResourceManager.Resources;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Core.Options;
 
 namespace Azure.Mcp.Tools.FileShares.Services;
@@ -435,7 +436,7 @@ public async Task<FileShareSnapshotInfo> GetSnapshotAsync(
 
         await foreach (var snapshotResource in snapshotCollection.WithCancellation(cancellationToken))
         {
-            if (snapshotResource.Data.Name.Equals(snapshotId, StringComparison.OrdinalIgnoreCase) ||
+            if (snapshotResource.Data.Name.Equals(snapshotId, StringComparisons.ResourceName) ||
                 snapshotResource.Data.Id.ToString().Equals(snapshotId, StringComparison.OrdinalIgnoreCase))
             {
                 return FileShareSnapshotInfo.FromResource(snapshotResource);

tools/Azure.Mcp.Tools.FoundryExtensions/src/Services/FoundryExtensionsService.cs

@@ -173,7 +173,7 @@ public async Task<KnowledgeIndexSchema> GetKnowledgeIndexSchema(
 
         // Find the index by name using async enumerable
         var index = await indexesClient.GetIndicesAsync(cancellationToken: cancellationToken)
-            .Where(i => string.Equals(i.Name, indexName, StringComparison.OrdinalIgnoreCase))
+            .Where(i => string.Equals(i.Name, indexName, StringComparisons.ResourceName))
             .FirstOrDefaultAsync(cancellationToken: cancellationToken);
 
         if (index == null)
@@ -648,7 +648,7 @@ public async Task<List<AiResourceInformation>> ListAiResourcesAsync(
             {
                 var resourceInfo = await BuildResourceInformation(account, subscriptionResource.Data.DisplayName, cancellationToken);
                 resources.Add(resourceInfo);
-                if (account.Data.Id.ResourceGroupName?.Equals(resourceGroup, StringComparison.OrdinalIgnoreCase) == true)
+                if (account.Data.Id.ResourceGroupName?.Equals(resourceGroup, StringComparisons.ResourceGroup) == true)
                 {
                     var retrieved = await BuildResourceInformation(account, subscriptionResource.Data.DisplayName, cancellationToken);
                     resources.Add(retrieved);

tools/Azure.Mcp.Tools.Monitor/src/Services/MonitorService.cs

@@ -492,7 +492,7 @@ private async Task<ActivityLogListResponse> MakeActivityLogRequestAsync(string u
         // Find the workspace
         var matchingWorkspace = workspaces.FirstOrDefault(w =>
             isId ? w.CustomerId.Equals(workspace, StringComparison.OrdinalIgnoreCase)
-                : w.Name.Equals(workspace, StringComparison.OrdinalIgnoreCase));
+                : w.Name.Equals(workspace, StringComparisons.ResourceName));
 
         if (matchingWorkspace == null)
         {

tools/Azure.Mcp.Tools.Monitor/src/Services/ResourceResolverService.cs

@@ -5,6 +5,7 @@
 using Azure.Mcp.Core.Services.Azure;
 using Azure.Mcp.Core.Services.Azure.Subscription;
 using Azure.Mcp.Core.Services.Azure.Tenant;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Core.Options;
 
 namespace Azure.Mcp.Tools.Monitor.Services;
@@ -42,7 +43,7 @@ public async Task<ResourceIdentifier> ResolveResourceIdAsync(
 
         // Get all resources matching the name
         var allMatchingResources = await subscriptionResource.GetGenericResourcesAsync(cancellationToken: cancellationToken)
-            .Where(r => r.Data.Name?.Equals(resourceName, StringComparison.OrdinalIgnoreCase) == true)
+            .Where(r => r.Data.Name?.Equals(resourceName, StringComparisons.ResourceName) == true)
             .ToListAsync(cancellationToken: cancellationToken);
 
         if (allMatchingResources.Count == 0)
@@ -57,7 +58,7 @@ public async Task<ResourceIdentifier> ResolveResourceIdAsync(
         if (!string.IsNullOrEmpty(resourceGroup))
         {
             filteredResources = filteredResources.Where(r =>
-                r.Data.Id?.ResourceGroupName?.Equals(resourceGroup, StringComparison.OrdinalIgnoreCase) == true);
+                r.Data.Id?.ResourceGroupName?.Equals(resourceGroup, StringComparisons.ResourceGroup) == true);
         }
 
         // Filter by resource type if provided

tools/Azure.Mcp.Tools.Search/src/Services/SearchService.cs

@@ -17,6 +17,7 @@
 using Azure.Search.Documents.KnowledgeBases.Models;
 using Azure.Search.Documents.Models;
 using Microsoft.Extensions.Logging;
+using Microsoft.Mcp.Core.Helpers;
 using Microsoft.Mcp.Core.Options;
 using Microsoft.Mcp.Core.Services.Azure.Authentication;
 using Microsoft.Mcp.Core.Services.Caching;
@@ -215,7 +216,7 @@ public async Task<List<KnowledgeBaseInfo>> ListKnowledgeBases(
             var result = await searchClient.GetKnowledgeBaseAsync(knowledgeBaseName, cancellationToken: cancellationToken);
             if (result?.Value != null)
             {
-                if (result.Value.Name.Equals(knowledgeBaseName, StringComparison.OrdinalIgnoreCase))
+                if (result.Value.Name.Equals(knowledgeBaseName, StringComparisons.ResourceName))
                 {
                     bases.Add(new(result.Value.Name, result.Value.Description, [.. result.Value.KnowledgeSources.Select(ks => ks.Name)]));
                 }