Add OutputSchema support to MCP tool definitions

Introduces an optional OutputSchema property to McpToolDefinition and updates AbpMcpServerTool and McpServerService to handle and register tools with output schemas. This enables tools to define and expose their output schema alongside input schema for improved contract clarity.

framework/src/Volo.Abp.Cli.Core/Volo/Abp/Cli/Commands/Models/McpToolDefinition.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Text.Json;
 
 namespace Volo.Abp.Cli.Commands.Models;
 
@@ -7,6 +8,7 @@ public class McpToolDefinition
     public string Name { get; set; }
     public string Description { get; set; }
     public McpToolInputSchema InputSchema { get; set; }
+    public JsonElement? OutputSchema { get; set; }
 }
 
 public class McpToolInputSchema

framework/src/Volo.Abp.Cli.Core/Volo/Abp/Cli/Commands/Services/AbpMcpServerTool.cs

@@ -13,17 +13,20 @@ internal class AbpMcpServerTool : McpServerTool
     private readonly string _name;
     private readonly string _description;
     private readonly JsonElement _inputSchema;
+    private readonly JsonElement? _outputSchema;
     private readonly Func<RequestContext<CallToolRequestParams>, CancellationToken, ValueTask<CallToolResult>> _handler;
 
     public AbpMcpServerTool(
         string name,
         string description,
         JsonElement inputSchema,
+        JsonElement? outputSchema,
         Func<RequestContext<CallToolRequestParams>, CancellationToken, ValueTask<CallToolResult>> handler)
     {
         _name = name;
         _description = description;
         _inputSchema = inputSchema;
+        _outputSchema = outputSchema;
         _handler = handler;
     }
 
@@ -31,7 +34,8 @@ internal class AbpMcpServerTool : McpServerTool
     {
         Name = _name,
         Description = _description,
-        InputSchema = _inputSchema
+        InputSchema = _inputSchema,
+        OutputSchema = _outputSchema
     };
 
     public override IReadOnlyList<object> Metadata => Array.Empty<object>();

framework/src/Volo.Abp.Cli.Core/Volo/Abp/Cli/Commands/Services/McpServerService.cs

@@ -82,7 +82,7 @@ public class McpServerService : ITransientDependency
             ["required"] = toolDef.InputSchema?.Required ?? new List<string>()
         };
 
-        RegisterTool(options, toolDef.Name, toolDef.Description, inputSchemaObject);
+        RegisterTool(options, toolDef.Name, toolDef.Description, inputSchemaObject, toolDef.OutputSchema);
     }
 
     private Dictionary<string, object> ConvertProperties(Dictionary<string, McpToolProperty> properties)
@@ -121,7 +121,8 @@ public class McpServerService : ITransientDependency
         McpServerOptions options,
         string name,
         string description,
-        object inputSchema)
+        object inputSchema,
+        JsonElement? outputSchema)
     {
         if (options.ToolCollection == null)
         {
@@ -132,6 +133,7 @@ public class McpServerService : ITransientDependency
             name,
             description,
             JsonSerializer.SerializeToElement(inputSchema),
+            outputSchema,
             (context, cancellationToken) => HandleToolInvocationAsync(name, context, cancellationToken)
         );