fix: restore Destructive = false on all MCP tool annotations

The MCP spec (and C# SDK) default destructiveHint to true.
Explicitly setting Destructive = false is required so clients
know these read-only book search tools are non-destructive.

Note: per spec, destructiveHint is 'only meaningful when
readOnlyHint == false', but the SDK still emits the value
on the wire so explicit false is the safe, correct choice.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: BenjaminMichaelis

EssentialCSharp.Web/Tools/BookContentTool.cs

@@ -1,4 +1,4 @@
-using System.ComponentModel;
+using System.ComponentModel;
 using System.Globalization;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -33,7 +33,7 @@ public BookContentTool(
         _searchService = serviceProvider.GetService<AISearchService>();
     }
 
-    [McpServerTool(Title = "Get Section Content", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get Section Content", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Retrieve the prose content of a specific book section identified by its slug/key (e.g., 'hello-world', 'creating-editing-compiling-and-running-c-source-code'). Returns the section text with code examples preserved. Use GetChapterSections to discover available slugs.")]
     public async Task<string> GetSectionContent(
         [Description("The section slug/key (e.g., 'hello-world'). Use GetChapterSections to get valid slugs.")] string sectionKey,
@@ -145,7 +145,7 @@ public async Task<string> GetSectionContent(
         return body.Length == 0 ? $"No content found after section heading '{mapping.RawHeading}'." : header.Append(body).ToString();
     }
 
-    [McpServerTool(Title = "Get Listing With Context", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get Listing With Context", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Retrieve a specific book listing's source code together with the semantic book content that explains it. Combines code from GetListingSourceCode with related explanatory text found via search. Ideal for understanding what a listing demonstrates.")]
     public async Task<string> GetListingWithContext(
         [Description("The chapter number of the listing.")] int chapter,
@@ -191,7 +191,7 @@ public async Task<string> GetListingWithContext(
         return sb.ToString();
     }
 
-    [McpServerTool(Title = "Get Navigation Context", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get Navigation Context", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Get the navigation context for a book section: its breadcrumb path, the previous and next sections, its parent section, and its sibling sections. Useful for understanding where a section sits in the book's structure.")]
     public string GetNavigationContext(
         [Description("The section slug/key (e.g., 'hello-world'). Use GetChapterSections to get valid slugs.")] string sectionKey)
@@ -325,7 +325,7 @@ public string GetNavigationContext(
         return sb.ToString();
     }
 
-    [McpServerTool(Title = "Get Chapter Summary", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get Chapter Summary", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Get a structural overview of a book chapter: its top-level section headings in reading order, and the coding guidelines associated with that chapter. Useful for understanding what a chapter covers before diving in.")]
     public string GetChapterSummary(
         [Description("The chapter number (e.g., 5 for Chapter 5).")] int chapter)

EssentialCSharp.Web/Tools/BookGuidelinesTool.cs

@@ -1,4 +1,4 @@
-using System.ComponentModel;
+using System.ComponentModel;
 using System.Globalization;
 using System.Text;
 using EssentialCSharp.Web.Services;
@@ -16,7 +16,7 @@ public BookGuidelinesTool(IGuidelinesService guidelinesService)
         _guidelinesService = guidelinesService;
     }
 
-    [McpServerTool(Title = "Get C# Guidelines", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get C# Guidelines", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Retrieve C# coding guidelines from the Essential C# book. Optionally filter by keyword, chapter number, or guideline type (do/consider/avoid/donot). The book contains guidelines covering naming conventions, error handling, LINQ, async/await, generics, and many other topics. Each guideline includes its chapter and subsection context.")]
     public string GetCSharpGuidelines(
         [Description("Optional keyword to filter guidelines by (searched in guideline text and subsection name).")] string? keyword = null,
@@ -67,7 +67,7 @@ public string GetCSharpGuidelines(
         return sb.ToString();
     }
 
-    [McpServerTool(Title = "Get Guidelines By Topic", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get Guidelines By Topic", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Search C# coding guidelines from the Essential C# book by topic or concept. More discoverable than filtering by chapter — finds all guidelines related to exceptions, naming, async, LINQ, generics, interfaces, and more. Results are ordered by relevance to the topic.")]
     public string GetGuidelinesByTopic(
         [Description("The topic or concept to search guidelines for (e.g., 'exception handling', 'naming', 'async', 'LINQ', 'generics', 'interface').")] string topic,

EssentialCSharp.Web/Tools/BookListingTool.cs

@@ -1,4 +1,4 @@
-using System.ComponentModel;
+using System.ComponentModel;
 using System.Globalization;
 using System.Text;
 using EssentialCSharp.Web.Services;
@@ -18,7 +18,7 @@ public BookListingTool(IListingSourceCodeService listingService, ISiteMappingSer
         _siteMappingService = siteMappingService;
     }
 
-    [McpServerTool(Title = "Get Listing Source Code", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get Listing Source Code", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Retrieve the complete source code for a specific numbered listing from the Essential C# book. Example: chapter=5, listing=3 retrieves Listing 5.3. Returns the code and its file type.")]
     public async Task<string> GetListingSourceCode(
         [Description("The chapter number containing the listing (e.g., 5 for Chapter 5).")] int chapter,
@@ -35,7 +35,7 @@ public async Task<string> GetListingSourceCode(
         return $"## Listing {response.ChapterNumber}.{response.ListingNumber}\n\n```{langHint}\n{response.Content}\n```";
     }
 
-    [McpServerTool(Title = "Search Listings By Code", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Search Listings By Code", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Search all code listings in the Essential C# book for a specific code pattern, keyword, or identifier. Searches actual C# source code (not prose). Useful for finding examples of Task.WhenAll, yield return, IDisposable, pattern matching, and similar code constructs.")]
     public async Task<string> SearchListingsByCode(
         [Description("The code pattern or keyword to search for in listing source code (case-insensitive substring match).")] string pattern,

EssentialCSharp.Web/Tools/BookSearchTool.cs

@@ -1,4 +1,4 @@
-using System.ComponentModel;
+using System.ComponentModel;
 using System.Globalization;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -35,7 +35,7 @@ public BookSearchTool(IServiceProvider serviceProvider, ISiteMappingService site
         _guidelinesService = guidelinesService;
     }
 
-    [McpServerTool(Title = "Search Book Content", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Search Book Content", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Search the Essential C# book content using semantic vector search. Returns relevant text chunks with chapter and heading context. Use this to find information about C# programming concepts covered in the book.")]
     public async Task<string> SearchBookContent(
         [Description("The search query describing the C# concept or topic to find in the book.")] string query,
@@ -87,7 +87,7 @@ public async Task<string> SearchBookContent(
         return sb.ToString();
     }
 
-    [McpServerTool(Title = "Get Chapter List", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get Chapter List", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Get the table of contents for the Essential C# book, listing all chapters and their sections with navigation links.")]
     public string GetChapterList()
     {
@@ -118,7 +118,7 @@ public string GetChapterList()
         return sb.ToString();
     }
 
-    [McpServerTool(Title = "Get Chapter Sections", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get Chapter Sections", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Get all sections and subsections in a specific chapter of the Essential C# book, in reading order. Returns each section's heading, slug, anchor link, and indent level. Use the returned slugs with other tools like GetSectionContent or GetNavigationContext.")]
     public string GetChapterSections(
         [Description("The chapter number (e.g., 5 for Chapter 5).")] int chapter)
@@ -150,7 +150,7 @@ public string GetChapterSections(
         return sb.ToString();
     }
 
-    [McpServerTool(Title = "Get Direct Content URL", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get Direct Content URL", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Get the canonical deep-link URL for a specific book section or subsection. Returns a clickable URL that navigates directly to the section. Use this to include precise references in responses.")]
     public string GetDirectContentUrl(
         [Description("The section slug/key (e.g., 'hello-world'). Use GetChapterSections or GetChapterList to find valid slugs.")] string sectionKey)
@@ -175,7 +175,7 @@ public string GetDirectContentUrl(
                $"URL: {url}";
     }
 
-    [McpServerTool(Title = "Get Book Metadata", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Get Book Metadata", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Get citation-quality metadata for the Essential C# book: title, authors, edition, C# version covered, ISBN, publisher, and website URL. Use this when generating citations or when asked which edition or C# version the book covers.")]
     public string GetBookMetadata()
     {
@@ -192,7 +192,7 @@ public string GetBookMetadata()
                 """;
     }
 
-    [McpServerTool(Title = "Lookup Concept", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Lookup Concept", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Find all sections in the Essential C# book that cover a specific C# concept. Combines section heading search with semantic vector search (when available) to give broad coverage. Returns section slugs, chapter numbers, and direct links.")]
     public async Task<string> LookupConcept(
         [Description("The C# concept, feature, or topic to find in the book (e.g., 'LINQ', 'async/await', 'pattern matching', 'generics').")] string concept,
@@ -267,7 +267,7 @@ public async Task<string> LookupConcept(
         return sb.ToString();
     }
 
-    [McpServerTool(Title = "Check Topic Coverage", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Check Topic Coverage", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Determine whether and how thoroughly the Essential C# book covers a given topic. Returns a coverage assessment: 'Comprehensive', 'Mentioned', or 'Not found in headings'. Use this before citing the book to calibrate confidence.")]
     public async Task<string> CheckTopicCoverage(
         [Description("The C# topic, feature, or concept to check (e.g., 'source generators', 'records', 'LINQ').")] string topic,
@@ -337,7 +337,7 @@ public async Task<string> CheckTopicCoverage(
         return sb.ToString();
     }
 
-    [McpServerTool(Title = "Find Book Help For Diagnostic", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Find Book Help For Diagnostic", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Find Essential C# book sections, content, and coding guidelines that help explain a C# compiler error, warning, or runtime exception. Accepts a CS diagnostic code (e.g., 'CS8600') or a plain description (e.g., 'null reference exception', 'cannot implicitly convert'). Returns relevant sections, explanatory prose, and related guidelines.")]
     public async Task<string> FindBookHelpForDiagnostic(
         [Description("A C# compiler diagnostic code (e.g., 'CS8600', 'CS0029') or a plain error description (e.g., 'null reference exception', 'async method lacks await').")] string diagnostic,
@@ -437,7 +437,7 @@ public async Task<string> FindBookHelpForDiagnostic(
         return sb.ToString();
     }
 
-    [McpServerTool(Title = "Find Related Sections", ReadOnly = true, Idempotent = true, OpenWorld = false),
+    [McpServerTool(Title = "Find Related Sections", ReadOnly = true, Destructive = false, Idempotent = true, OpenWorld = false),
      Description("Find other sections in the Essential C# book that are semantically related to a given section. Uses the section heading as a search query to discover thematically connected content across the entire book. Requires AI services to be configured.")]
     public async Task<string> FindRelatedSections(
         [Description("The section slug/key to find related content for (e.g., 'async-await'). Use GetChapterSections to get valid slugs.")] string sectionKey,