Add execution plan analysis MCP tools to Dashboard and Lite

Dashboard/Mcp/McpHostService.cs

@@ -81,7 +81,8 @@ protected override async Task ExecuteAsync(CancellationToken stoppingToken)
                 .WithTools<McpTempDbTools>()
                 .WithTools<McpPerfmonTools>()
                 .WithTools<McpAlertTools>()
-                .WithTools<McpJobTools>();
+                .WithTools<McpJobTools>()
+                .WithTools<McpPlanTools>();
 
             _app = builder.Build();
             _app.MapMcp();

Dashboard/Mcp/McpInstructions.cs

@@ -103,6 +103,25 @@ You are connected to a SQL Server performance monitoring tool via Performance Mo
         |------|---------|----------------|
         | `get_running_jobs` | Currently running SQL Agent jobs with duration vs historical average/p95 | `server_name` |
 
+        ### Execution Plan Analysis Tools
+        | Tool | Purpose | Key Parameters |
+        |------|---------|----------------|
+        | `analyze_query_plan` | Analyze plan from plan cache by query_hash | `query_hash` (required), `server_name` |
+        | `analyze_procedure_plan` | Analyze procedure plan by sql_handle | `sql_handle` (required), `server_name` |
+        | `analyze_query_store_plan` | Analyze plan from Query Store by database + query_id | `database_name` (required), `query_id` (required), `server_name` |
+        | `analyze_plan_xml` | Analyze raw showplan XML directly | `plan_xml` (required) |
+        | `get_plan_xml` | Get raw showplan XML by query_hash | `query_hash` (required), `server_name` |
+
+        Plan analysis detects 31 performance anti-patterns including:
+        - Missing indexes with CREATE statements and impact scores
+        - Non-SARGable predicates, implicit conversions, data type mismatches
+        - Memory grant issues, spills to TempDB
+        - Parallelism problems: serial plan reasons, thread skew, ineffective parallelism
+        - Parameter sniffing (compiled vs runtime value mismatches)
+        - Expensive operators: key lookups, scans with residual predicates, eager spools
+        - Join issues: OR clauses, high nested loop executions, many-to-many merge joins
+        - UDF execution overhead, table variable usage, CTE multiple references
+
         ## Recommended Workflow
 
         1. **Start**: `list_servers` — see what's monitored and which servers are online
@@ -117,6 +136,7 @@ You are connected to a SQL Server performance monitoring tool via Performance Mo
            - I/O latency → `get_file_io_stats` → `get_file_io_trend`
            - TempDB pressure → `get_tempdb_trend`
         5. **Query investigation**: After finding a problematic query via `get_top_queries_by_cpu`, `get_query_store_top`, or `get_expensive_queries`, use `get_query_trend` with its `query_hash` to see performance history
+        6. **Plan analysis**: Use `analyze_query_plan` with the `query_hash` from step 5 to get detailed plan analysis with warnings, missing indexes, and optimization recommendations
 
         ## Wait Type to Tool Mapping
 

Dashboard/Mcp/McpPlanTools.cs

@@ -0,0 +1,275 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Linq;
+using System.Text.Json;
+using System.Threading.Tasks;
+using ModelContextProtocol.Server;
+using PerformanceMonitorDashboard.Models;
+using PerformanceMonitorDashboard.Services;
+
+#pragma warning disable CA1707 // MCP tools use snake_case naming convention
+
+namespace PerformanceMonitorDashboard.Mcp;
+
+[McpServerToolType]
+public sealed class McpPlanTools
+{
+    [McpServerTool(Name = "analyze_query_plan"), Description(
+        "Analyzes an execution plan from query stats (plan cache) by query_hash. " +
+        "Use after get_top_queries_by_cpu to understand why a query is expensive. " +
+        "Returns warnings, missing indexes, parameters, memory grants, and top operators.")]
+    public static async Task<string> AnalyzeQueryPlan(
+        ServerManager serverManager,
+        DatabaseServiceRegistry registry,
+        [Description("The query_hash value from get_top_queries_by_cpu.")] string query_hash,
+        [Description("Server name or display name.")] string? server_name = null)
+    {
+        var resolved = ServerResolver.Resolve(serverManager, registry, server_name);
+        if (resolved == null)
+            return $"Could not resolve server. Available servers:\n{ServerResolver.ListAvailableServers(serverManager)}";
+
+        try
+        {
+            var xml = await resolved.Value.Service.GetPlanXmlByQueryHashAsync(query_hash);
+            if (string.IsNullOrEmpty(xml))
+                return $"No plan found for query_hash '{query_hash}'. The query may have been evicted from the plan cache since the last collection.";
+
+            return BuildAnalysisResult(xml, resolved.Value.ServerName, "query_stats", query_hash);
+        }
+        catch (Exception ex)
+        {
+            return McpHelpers.FormatError("analyze_query_plan", ex);
+        }
+    }
+
+    [McpServerTool(Name = "analyze_procedure_plan"), Description(
+        "Analyzes an execution plan from procedure stats by sql_handle. " +
+        "Use after get_top_procedures_by_cpu to understand why a procedure is expensive. " +
+        "Returns warnings, missing indexes, parameters, memory grants, and top operators.")]
+    public static async Task<string> AnalyzeProcedurePlan(
+        ServerManager serverManager,
+        DatabaseServiceRegistry registry,
+        [Description("The sql_handle value from get_top_procedures_by_cpu.")] string sql_handle,
+        [Description("Server name or display name.")] string? server_name = null)
+    {
+        var resolved = ServerResolver.Resolve(serverManager, registry, server_name);
+        if (resolved == null)
+            return $"Could not resolve server. Available servers:\n{ServerResolver.ListAvailableServers(serverManager)}";
+
+        try
+        {
+            var xml = await resolved.Value.Service.GetProcedurePlanXmlBySqlHandleAsync(sql_handle);
+            if (string.IsNullOrEmpty(xml))
+                return $"No plan found for sql_handle '{sql_handle}'. The procedure may have been evicted from the plan cache since the last collection.";
+
+            return BuildAnalysisResult(xml, resolved.Value.ServerName, "procedure_stats", sql_handle);
+        }
+        catch (Exception ex)
+        {
+            return McpHelpers.FormatError("analyze_procedure_plan", ex);
+        }
+    }
+
+    [McpServerTool(Name = "analyze_query_store_plan"), Description(
+        "Analyzes an execution plan from Query Store by database name and query ID. " +
+        "Use after get_query_store_top to understand why a query is expensive. " +
+        "Returns warnings, missing indexes, parameters, memory grants, and top operators.")]
+    public static async Task<string> AnalyzeQueryStorePlan(
+        ServerManager serverManager,
+        DatabaseServiceRegistry registry,
+        [Description("The database_name from get_query_store_top.")] string database_name,
+        [Description("The query_id from get_query_store_top.")] long query_id,
+        [Description("Server name or display name.")] string? server_name = null)
+    {
+        var resolved = ServerResolver.Resolve(serverManager, registry, server_name);
+        if (resolved == null)
+            return $"Could not resolve server. Available servers:\n{ServerResolver.ListAvailableServers(serverManager)}";
+
+        try
+        {
+            var xml = await resolved.Value.Service.GetQueryStorePlanXmlAsync(database_name, query_id);
+            if (string.IsNullOrEmpty(xml))
+                return $"No plan found for query_id {query_id} in database '{database_name}'. Query Store may not be enabled or the query may have been purged.";
+
+            return BuildAnalysisResult(xml, resolved.Value.ServerName, "query_store", $"{database_name}:{query_id}");
+        }
+        catch (Exception ex)
+        {
+            return McpHelpers.FormatError("analyze_query_store_plan", ex);
+        }
+    }
+
+    [McpServerTool(Name = "analyze_plan_xml"), Description(
+        "Analyzes raw showplan XML directly. Use when you have plan XML from any source " +
+        "(clipboard, file, another tool). Returns warnings, missing indexes, parameters, " +
+        "memory grants, and top operators.")]
+    public static string AnalyzePlanXml(
+        [Description("Raw showplan XML content.")] string plan_xml)
+    {
+        if (string.IsNullOrWhiteSpace(plan_xml))
+            return "No plan XML provided.";
+
+        try
+        {
+            return BuildAnalysisResult(plan_xml, null, "xml", null);
+        }
+        catch (Exception ex)
+        {
+            return McpHelpers.FormatError("analyze_plan_xml", ex);
+        }
+    }
+
+    [McpServerTool(Name = "get_plan_xml"), Description(
+        "Returns the raw showplan XML for a query identified by query_hash. " +
+        "Use when you need to inspect plan details not captured in the structured analysis. " +
+        "Truncated at 500KB.")]
+    public static async Task<string> GetPlanXml(
+        ServerManager serverManager,
+        DatabaseServiceRegistry registry,
+        [Description("The query_hash value from get_top_queries_by_cpu.")] string query_hash,
+        [Description("Server name or display name.")] string? server_name = null)
+    {
+        var resolved = ServerResolver.Resolve(serverManager, registry, server_name);
+        if (resolved == null)
+            return $"Could not resolve server. Available servers:\n{ServerResolver.ListAvailableServers(serverManager)}";
+
+        try
+        {
+            var xml = await resolved.Value.Service.GetPlanXmlByQueryHashAsync(query_hash);
+            if (string.IsNullOrEmpty(xml))
+                return $"No plan found for query_hash '{query_hash}'.";
+
+            return McpHelpers.Truncate(xml, 512_000) ?? "No plan XML available.";
+        }
+        catch (Exception ex)
+        {
+            return McpHelpers.FormatError("get_plan_xml", ex);
+        }
+    }
+
+    /// <summary>
+    /// Parses plan XML, runs the analyzer, and builds a structured JSON result.
+    /// </summary>
+    private static string BuildAnalysisResult(string xml, string? serverName, string source, string? identifier)
+    {
+        var plan = ShowPlanParser.Parse(xml);
+        PlanAnalyzer.Analyze(plan);
+
+        var statements = plan.Batches
+            .SelectMany(b => b.Statements)
+            .Where(s => s.RootNode != null)
+            .Select(s =>
+            {
+                var allNodes = new List<PlanNode>();
+                CollectNodes(s.RootNode!, allNodes);
+
+                var nodeWarnings = allNodes
+                    .SelectMany(n => n.Warnings)
+                    .ToList();
+                var stmtWarnings = s.PlanWarnings;
+                var allWarnings = stmtWarnings.Concat(nodeWarnings).ToList();
+
+                var hasActuals = allNodes.Any(n => n.HasActualStats);
+                var topOps = (hasActuals
+                        ? allNodes.OrderByDescending(n => n.ActualElapsedMs)
+                        : allNodes.OrderByDescending(n => n.CostPercent))
+                    .Take(10)
+                    .Select(n => new
+                    {
+                        node_id = n.NodeId,
+                        physical_op = n.PhysicalOp,
+                        logical_op = n.LogicalOp,
+                        cost_percent = n.CostPercent,
+                        estimated_rows = n.EstimateRows,
+                        actual_rows = n.HasActualStats ? n.ActualRows : (long?)null,
+                        actual_elapsed_ms = n.HasActualStats ? n.ActualElapsedMs : (long?)null,
+                        actual_cpu_ms = n.HasActualStats ? n.ActualCPUMs : (long?)null,
+                        logical_reads = n.HasActualStats ? n.ActualLogicalReads : (long?)null,
+                        object_name = n.ObjectName,
+                        index_name = n.IndexName,
+                        predicate = McpHelpers.Truncate(n.Predicate, 500),
+                        seek_predicates = McpHelpers.Truncate(n.SeekPredicates, 500),
+                        warning_count = n.Warnings.Count
+                    });
+
+                return new
+                {
+                    statement_text = McpHelpers.Truncate(s.StatementText, 2000),
+                    statement_type = s.StatementType,
+                    estimated_cost = Math.Round(s.StatementSubTreeCost, 4),
+                    dop = s.DegreeOfParallelism,
+                    serial_reason = s.NonParallelPlanReason,
+                    compile_cpu_ms = s.CompileCPUMs,
+                    compile_memory_kb = s.CompileMemoryKB,
+                    cardinality_model = s.CardinalityEstimationModelVersion,
+                    query_hash = s.QueryHash,
+                    query_plan_hash = s.QueryPlanHash,
+                    has_actual_stats = hasActuals,
+                    warnings = allWarnings.Select(w => new
+                    {
+                        severity = w.Severity.ToString(),
+                        type = w.WarningType,
+                        message = w.Message
+                    }),
+                    warning_count = allWarnings.Count,
+                    critical_count = allWarnings.Count(w => w.Severity == PlanWarningSeverity.Critical),
+                    missing_indexes = s.MissingIndexes.Select(idx => new
+                    {
+                        table = $"{idx.Schema}.{idx.Table}",
+                        database = idx.Database,
+                        impact = idx.Impact,
+                        equality_columns = idx.EqualityColumns,
+                        inequality_columns = idx.InequalityColumns,
+                        include_columns = idx.IncludeColumns,
+                        create_statement = idx.CreateStatement
+                    }),
+                    parameters = s.Parameters.Select(p => new
+                    {
+                        name = p.Name,
+                        data_type = p.DataType,
+                        compiled_value = p.CompiledValue,
+                        runtime_value = p.RuntimeValue,
+                        sniffing_mismatch = p.CompiledValue != null && p.RuntimeValue != null
+                            && p.CompiledValue != p.RuntimeValue
+                    }),
+                    memory_grant = s.MemoryGrant == null ? null : new
+                    {
+                        requested_kb = s.MemoryGrant.RequestedMemoryKB,
+                        granted_kb = s.MemoryGrant.GrantedMemoryKB,
+                        max_used_kb = s.MemoryGrant.MaxUsedMemoryKB,
+                        desired_kb = s.MemoryGrant.DesiredMemoryKB,
+                        grant_wait_ms = s.MemoryGrant.GrantWaitTimeMs,
+                        feedback = s.MemoryGrant.IsMemoryGrantFeedbackAdjusted
+                    },
+                    top_operators = topOps
+                };
+            })
+            .ToList();
+
+        var totalWarnings = statements.Sum(s => s.warning_count);
+        var totalCritical = statements.Sum(s => s.critical_count);
+        var totalMissing = statements.Sum(s => s.missing_indexes.Count());
+
+        var result = new
+        {
+            server = serverName,
+            source,
+            identifier,
+            statement_count = statements.Count,
+            total_warnings = totalWarnings,
+            total_critical = totalCritical,
+            total_missing_indexes = totalMissing,
+            statements
+        };
+
+        return JsonSerializer.Serialize(result, McpHelpers.JsonOptions);
+    }
+
+    private static void CollectNodes(PlanNode node, List<PlanNode> nodes)
+    {
+        nodes.Add(node);
+        foreach (var child in node.Children)
+            CollectNodes(child, nodes);
+    }
+}

Dashboard/Services/DatabaseService.QueryPerformance.cs

@@ -2445,6 +2445,58 @@ FROM collect.query_stats AS qs
             return result == DBNull.Value || result == null ? null : (string)result;
         }
 
+        /// <summary>
+        /// Fetches the most recent plan XML for a query identified by query_hash.
+        /// Used by MCP plan analysis tools.
+        /// </summary>
+        public async Task<string?> GetPlanXmlByQueryHashAsync(string queryHash)
+        {
+            await using var tc = await OpenThrottledConnectionAsync();
+            var connection = tc.Connection;
+
+            string query = @"
+        SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
+
+        SELECT TOP (1)
+            CAST(DECOMPRESS(qs.query_plan_text) AS nvarchar(max))
+        FROM collect.query_stats AS qs
+        WHERE qs.query_hash = CONVERT(binary(8), @queryHash, 1)
+        ORDER BY qs.last_execution_time DESC;";
+
+            using var command = new SqlCommand(query, connection);
+            command.CommandTimeout = 120;
+            command.Parameters.Add(new SqlParameter("@queryHash", SqlDbType.NVarChar, 20) { Value = queryHash });
+
+            var result = await command.ExecuteScalarAsync();
+            return result == DBNull.Value || result == null ? null : (string)result;
+        }
+
+        /// <summary>
+        /// Fetches the most recent plan XML for a procedure identified by sql_handle.
+        /// Used by MCP plan analysis tools.
+        /// </summary>
+        public async Task<string?> GetProcedurePlanXmlBySqlHandleAsync(string sqlHandle)
+        {
+            await using var tc = await OpenThrottledConnectionAsync();
+            var connection = tc.Connection;
+
+            string query = @"
+        SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
+
+        SELECT TOP (1)
+            CAST(DECOMPRESS(ps.query_plan_text) AS nvarchar(max))
+        FROM collect.procedure_stats AS ps
+        WHERE ps.sql_handle = CONVERT(varbinary(64), @sqlHandle, 1)
+        ORDER BY ps.last_execution_time DESC;";
+
+            using var command = new SqlCommand(query, connection);
+            command.CommandTimeout = 120;
+            command.Parameters.Add(new SqlParameter("@sqlHandle", SqlDbType.NVarChar, 130) { Value = sqlHandle });
+
+            var result = await command.ExecuteScalarAsync();
+            return result == DBNull.Value || result == null ? null : (string)result;
+        }
+
         /// <summary>
         /// Gets execution count trends from query stats deltas, aggregated by collection time.
         /// </summary>

Lite/Mcp/McpHostService.cs

@@ -71,7 +71,8 @@ protected override async Task ExecuteAsync(CancellationToken stoppingToken)
                 .WithTools<McpTempDbTools>()
                 .WithTools<McpPerfmonTools>()
                 .WithTools<McpAlertTools>()
-                .WithTools<McpJobTools>();
+                .WithTools<McpJobTools>()
+                .WithTools<McpPlanTools>();
 
             _app = builder.Build();
             _app.MapMcp();