fix(tarko): improve mcp client connection failure handling

- Throw errors instead of returning empty arrays in MCPClient.listTools()
- Add tool count validation in MCPClientV2.initialize() to detect connection failures
- Prevent silent failures when MCP server connections fail

Author: ulivz

multimodal/tarko/mcp-agent/src/mcp-client-v2.ts

@@ -47,6 +47,12 @@ export class MCPClientV2 implements IMCPClient {
       this.logger.info(`Initializing MCP client v2 for ${this.serverName}`);
       await this.v2Client.init();
       this.tools = await this.v2Client.listTools(this.serverName as string);
+      
+      // Validate that we got tools - if 0 tools, this likely indicates a connection failure
+      if (this.tools.length === 0) {
+        throw new Error(`MCP server ${this.serverName} connection failed: no tools available`);
+      }
+      
       this.isInitialized = true;
       this.logger.success(
         `MCP client v2 initialized successfully for ${this.serverName}, found ${this.tools.length} tools`,

packages/agent-infra/mcp-client/src/index.ts

@@ -557,14 +557,19 @@ export class MCPClient<
               `[MCP] Error listing tools for ${clientName}:`,
               error,
             );
+            // Re-throw error for specific server when serverName is provided
+            if (serverName === clientName) {
+              throw error;
+            }
           }
         }
         this.log('info', `[MCP] Total tools listed: ${allTools.length}`);
         return allTools;
       }
     } catch (error) {
       this.log('error', '[MCP] Error listing tools:', error);
-      return [];
+      // Don't return empty array for critical failures, re-throw the error
+      throw error;
     }
   }