Add server-level description field to MCP runtime configuration

src/Azure.DataApiBuilder.Mcp/Core/McpStdioServer.cs

@@ -3,7 +3,9 @@
 using System.Security.Claims;
 using System.Text;
 using System.Text.Json;
+using Azure.DataApiBuilder.Config.ObjectModel;
 using Azure.DataApiBuilder.Core.AuthenticationHelpers.AuthenticationSimulator;
+using Azure.DataApiBuilder.Core.Configurations;
 using Azure.DataApiBuilder.Mcp.Model;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Configuration;
@@ -161,25 +163,46 @@ private void HandleInitialize(JsonElement? id)
             // Extract the actual id value from the request
             object? requestId = id.HasValue ? GetIdValue(id.Value) : null;
 
+            // Get the description from runtime config if available
+            string? instructions = null;
+            RuntimeConfigProvider? runtimeConfigProvider = _serviceProvider.GetService<RuntimeConfigProvider>();
+            if (runtimeConfigProvider != null)
+            {
+                try
+                {
+                    RuntimeConfig runtimeConfig = runtimeConfigProvider.GetConfig();
+                    instructions = runtimeConfig.Runtime?.Mcp?.Description;
+                }
+                catch (Exception ex)
+                {
+                    // Log to stderr for diagnostics and rethrow to avoid masking configuration errors
+                    Console.Error.WriteLine($"[MCP WARNING] Failed to retrieve MCP description from config: {ex.Message}");
+                    throw;
+                }
+            }
+
             // Create the initialize response
+            var result = new
+            {
+                protocolVersion = _protocolVersion,
+                capabilities = new
+                {
+                    tools = new { listChanged = true },
+                    logging = new { }
+                },
+                serverInfo = new
+                {
+                    name = "Data API Builder",
+                    version = "1.0.0"
+                },
+                instructions = !string.IsNullOrWhiteSpace(instructions) ? instructions : null
+            };
+
             var response = new
             {
                 jsonrpc = "2.0",
                 id = requestId,
-                result = new
-                {
-                    protocolVersion = _protocolVersion,
-                    capabilities = new
-                    {
-                        tools = new { listChanged = true },
-                        logging = new { }
-                    },
-                    serverInfo = new
-                    {
-                        name = "Data API Builder",
-                        version = "1.0.0"
-                    }
-                }
+                result
             };
 
             string json = JsonSerializer.Serialize(response);

src/Cli.Tests/ConfigureOptionsTests.cs

@@ -926,6 +926,63 @@ public void TestFailureWhenAddingSetSessionContextToMySQLDatabase()
             Assert.IsFalse(isSuccess);
         }
 
+        /// <summary>
+        /// Tests that running "dab configure --runtime.mcp.description {value}" on a config with various values results
+        /// in runtime config update. Takes in updated value for mcp.description and 
+        /// validates whether the runtime config reflects those updated values
+        /// </summary>
+        [DataTestMethod]
+        [DataRow("This MCP provides access to the Products database and should be used to answer product-related or inventory-related questions from the user.", DisplayName = "Set MCP description.")]
+        [DataRow("Use this server for customer data queries.", DisplayName = "Set MCP description with short text.")]
+        public void TestUpdateDescriptionForMcpSettings(string descriptionValue)
+        {
+            // Arrange -> all the setup which includes creating options.
+            SetupFileSystemWithInitialConfig(INITIAL_CONFIG);
+
+            // Act: Attempts to update mcp.description value
+            ConfigureOptions options = new(
+                runtimeMcpDescription: descriptionValue,
+                config: TEST_RUNTIME_CONFIG_FILE
+            );
+            bool isSuccess = TryConfigureSettings(options, _runtimeConfigLoader!, _fileSystem!);
+
+            // Assert: Validate the Description is updated
+            Assert.IsTrue(isSuccess);
+            string updatedConfig = _fileSystem!.File.ReadAllText(TEST_RUNTIME_CONFIG_FILE);
+            Assert.IsTrue(RuntimeConfigLoader.TryParseConfig(updatedConfig, out RuntimeConfig? runtimeConfig));
+            Assert.IsNotNull(runtimeConfig.Runtime?.Mcp?.Description);
+            Assert.AreEqual(descriptionValue, runtimeConfig.Runtime.Mcp.Description);
+        }
+
+        /// <summary>
+        /// Tests that the MCP description can be added to a config that doesn't already have one
+        /// </summary>
+        [TestMethod]
+        public void TestAddDescriptionToMcpSettings()
+        {
+            // Arrange
+            SetupFileSystemWithInitialConfig(INITIAL_CONFIG);
+
+            // Initial config should not have a description
+            Assert.IsTrue(RuntimeConfigLoader.TryParseConfig(INITIAL_CONFIG, out RuntimeConfig? config));
+            Assert.IsNull(config.Runtime?.Mcp?.Description);
+
+            // Act: Add description
+            string descriptionValue = "This is a test description for MCP server.";
+            ConfigureOptions options = new(
+                runtimeMcpDescription: descriptionValue,
+                config: TEST_RUNTIME_CONFIG_FILE
+            );
+            bool isSuccess = TryConfigureSettings(options, _runtimeConfigLoader!, _fileSystem!);
+
+            // Assert: Validate the Description is added
+            Assert.IsTrue(isSuccess);
+            string updatedConfig = _fileSystem!.File.ReadAllText(TEST_RUNTIME_CONFIG_FILE);
+            Assert.IsTrue(RuntimeConfigLoader.TryParseConfig(updatedConfig, out RuntimeConfig? runtimeConfig));
+            Assert.IsNotNull(runtimeConfig.Runtime?.Mcp?.Description);
+            Assert.AreEqual(descriptionValue, runtimeConfig.Runtime.Mcp.Description);
+        }
+
         /// <summary>
         /// Sets up the mock file system with an initial configuration file.
         /// This method adds a config file to the mock file system and verifies its existence.

src/Cli/Commands/ConfigureOptions.cs

@@ -38,6 +38,7 @@ public ConfigureOptions(
             bool? runtimeRestRequestBodyStrict = null,
             bool? runtimeMcpEnabled = null,
             string? runtimeMcpPath = null,
+            string? runtimeMcpDescription = null,
             bool? runtimeMcpDmlToolsEnabled = null,
             bool? runtimeMcpDmlToolsDescribeEntitiesEnabled = null,
             bool? runtimeMcpDmlToolsCreateRecordEnabled = null,
@@ -93,6 +94,7 @@ public ConfigureOptions(
             // Mcp
             RuntimeMcpEnabled = runtimeMcpEnabled;
             RuntimeMcpPath = runtimeMcpPath;
+            RuntimeMcpDescription = runtimeMcpDescription;
             RuntimeMcpDmlToolsEnabled = runtimeMcpDmlToolsEnabled;
             RuntimeMcpDmlToolsDescribeEntitiesEnabled = runtimeMcpDmlToolsDescribeEntitiesEnabled;
             RuntimeMcpDmlToolsCreateRecordEnabled = runtimeMcpDmlToolsCreateRecordEnabled;
@@ -180,6 +182,9 @@ public ConfigureOptions(
         [Option("runtime.mcp.path", Required = false, HelpText = "Customize DAB's MCP endpoint path. Default: '/mcp' Conditions: Prefix path with '/'.")]
         public string? RuntimeMcpPath { get; }
 
+        [Option("runtime.mcp.description", Required = false, HelpText = "Set the MCP server description to be exposed in the initialize response.")]
+        public string? RuntimeMcpDescription { get; }
+
         [Option("runtime.mcp.dml-tools.enabled", Required = false, HelpText = "Enable DAB's MCP DML tools endpoint. Default: true (boolean).")]
         public bool? RuntimeMcpDmlToolsEnabled { get; }
 

src/Cli/ConfigGenerator.cs

@@ -797,7 +797,15 @@ private static bool TryUpdateConfiguredRuntimeOptions(
 
             // MCP: Enabled and Path
             if (options.RuntimeMcpEnabled != null ||
-                options.RuntimeMcpPath != null)
+                options.RuntimeMcpPath != null ||
+                options.RuntimeMcpDescription != null ||
+                options.RuntimeMcpDmlToolsEnabled != null ||
+                options.RuntimeMcpDmlToolsDescribeEntitiesEnabled != null ||
+                options.RuntimeMcpDmlToolsCreateRecordEnabled != null ||
+                options.RuntimeMcpDmlToolsReadRecordsEnabled != null ||
+                options.RuntimeMcpDmlToolsUpdateRecordEnabled != null ||
+                options.RuntimeMcpDmlToolsDeleteRecordEnabled != null ||
+                options.RuntimeMcpDmlToolsExecuteEntityEnabled != null)
             {
                 McpRuntimeOptions updatedMcpOptions = runtimeConfig?.Runtime?.Mcp ?? new();
                 bool status = TryUpdateConfiguredMcpValues(options, ref updatedMcpOptions);
@@ -1053,6 +1061,14 @@ private static bool TryUpdateConfiguredMcpValues(
                     }
                 }
 
+                // Runtime.Mcp.Description
+                updatedValue = options?.RuntimeMcpDescription;
+                if (updatedValue != null)
+                {
+                    updatedMcpOptions = updatedMcpOptions! with { Description = (string)updatedValue };
+                    _logger.LogInformation("Updated RuntimeConfig with Runtime.Mcp.Description as '{updatedValue}'", updatedValue);
+                }
+
                 // Handle DML tools configuration
                 bool hasToolUpdates = false;
                 DmlToolsConfig? currentDmlTools = updatedMcpOptions?.DmlTools;

src/Config/Converters/McpRuntimeOptionsConverterFactory.cs

@@ -65,12 +65,13 @@ internal McpRuntimeOptionsConverter(DeserializationVariableReplacementSettings?
                 bool enabled = true;
                 string? path = null;
                 DmlToolsConfig? dmlTools = null;
+                string? description = null;
 
                 while (reader.Read())
                 {
                     if (reader.TokenType == JsonTokenType.EndObject)
                     {
-                        return new McpRuntimeOptions(enabled, path, dmlTools);
+                        return new McpRuntimeOptions(enabled, path, dmlTools, description);
                     }
 
                     string? propertyName = reader.GetString();
@@ -98,6 +99,14 @@ internal McpRuntimeOptionsConverter(DeserializationVariableReplacementSettings?
                             dmlTools = dmlToolsConfigConverter.Read(ref reader, typeToConvert, options);
                             break;
 
+                        case "description":
+                            if (reader.TokenType is not JsonTokenType.Null)
+                            {
+                                description = reader.DeserializeString(_replacementSettings);
+                            }
+
+                            break;
+
                         default:
                             throw new JsonException($"Unexpected property {propertyName}");
                     }
@@ -134,6 +143,13 @@ public override void Write(Utf8JsonWriter writer, McpRuntimeOptions value, JsonS
                 dmlToolsOptionsConverter.Write(writer, value.DmlTools, options);
             }
 
+            // Write description if it's provided
+            if (value is not null && !string.IsNullOrWhiteSpace(value.Description))
+            {
+                writer.WritePropertyName("description");
+                JsonSerializer.Serialize(writer, value.Description, options);
+            }
+
             writer.WriteEndObject();
         }
     }

src/Config/ObjectModel/McpRuntimeOptions.cs

@@ -30,11 +30,18 @@ public record McpRuntimeOptions
     [JsonConverter(typeof(DmlToolsConfigConverter))]
     public DmlToolsConfig? DmlTools { get; init; }
 
+    /// <summary>
+    /// Description of the MCP server to be exposed in the initialize response
+    /// </summary>
+    [JsonPropertyName("description")]
+    public string? Description { get; init; }
+
     [JsonConstructor]
     public McpRuntimeOptions(
         bool? Enabled = null,
         string? Path = null,
-        DmlToolsConfig? DmlTools = null)
+        DmlToolsConfig? DmlTools = null,
+        string? Description = null)
     {
         this.Enabled = Enabled ?? true;
 
@@ -58,6 +65,8 @@ public McpRuntimeOptions(
         {
             this.DmlTools = DmlTools;
         }
+
+        this.Description = Description;
     }
 
     /// <summary>