Refactor MCP tool response handling for consistency

src/mcp/tools/fileSystemReadDirectoryTool.ts

@@ -4,6 +4,7 @@
 import type { CallToolResult } from '@modelcontextprotocol/sdk/types.js';
 import { z } from 'zod';
 import { logger } from '../../shared/logger.js';
+import { buildMcpToolErrorResponse, buildMcpToolSuccessResponse } from './mcpToolRuntime.js';
 
 /**
  * Register file system directory listing tool
@@ -28,41 +29,19 @@
 
         // Ensure path is absolute
         if (!path.isAbsolute(directoryPath)) {
-          return {
-            isError: true,
-            content: [
-              {
-                type: 'text',
-                text: `Error: Path must be absolute. Received: ${directoryPath}`,
-              },
-            ],
-          };
+          return buildMcpToolErrorResponse([`Error: Path must be absolute. Received: ${directoryPath}`]);
         }
 
         // Check if directory exists
         try {
           const stats = await fs.stat(directoryPath);
           if (!stats.isDirectory()) {
-            return {
-              isError: true,
-              content: [
-                {
-                  type: 'text',
-                  text: `Error: The specified path is not a directory: ${directoryPath}. Use file_system_read_file for files.`,
-                },
-              ],
-            };
+            return buildMcpToolErrorResponse([
+              `Error: The specified path is not a directory: ${directoryPath}. Use file_system_read_file for files.`,
+            ]);
           }
         } catch {
-          return {
-            isError: true,
-            content: [
-              {
-                type: 'text',
-                text: `Error: Directory not found at path: ${directoryPath}`,
-              },
-            ],
-          };
+          return buildMcpToolErrorResponse([`Error: Directory not found at path: ${directoryPath}`]);
         }
 
         // Read directory contents
@@ -71,29 +50,12 @@
           .map((entry) => `${entry.isDirectory() ? '[DIR]' : '[FILE]'} ${entry.name}`)
           .join('\n');
 
-        return {
-          content: [
-            {
-              type: 'text',
-              text: `Contents of ${directoryPath}:`,
-            },
-            {
-              type: 'text',
-              text: formatted || '(empty directory)',
-            },
-          ],
-        };
+        return buildMcpToolSuccessResponse([`Contents of ${directoryPath}:`, formatted || '(empty directory)']);
       } catch (error) {
         logger.error(`Error in file_system_read_directory tool: ${error}`);
-        return {
-          isError: true,
-          content: [
-            {
-              type: 'text',
-              text: `Error listing directory: ${error instanceof Error ? error.message : String(error)}`,
-            },
-          ],
-        };
+        return buildMcpToolErrorResponse([
+          `Error listing directory: ${error instanceof Error ? error.message : String(error)}`,
+        ]);
       }
     },
   );

src/mcp/tools/fileSystemReadFileTool.ts

@@ -6,6 +6,7 @@
 import type { SuspiciousFileResult } from '../../core/security/securityCheck.js';
 import { createSecretLintConfig, runSecretLint } from '../../core/security/workers/securityCheckWorker.js';
 import { logger } from '../../shared/logger.js';
+import { buildMcpToolErrorResponse, buildMcpToolSuccessResponse } from './mcpToolRuntime.js';
 
 /**
  * Register file system read file tool with security checks
@@ -30,44 +31,22 @@
 
         // Ensure path is absolute
         if (!path.isAbsolute(filePath)) {
-          return {
-            isError: true,
-            content: [
-              {
-                type: 'text',
-                text: `Error: Path must be absolute. Received: ${filePath}`,
-              },
-            ],
-          };
+          return buildMcpToolErrorResponse([`Error: Path must be absolute. Received: ${filePath}`]);
         }
 
         // Check if file exists
         try {
           await fs.access(filePath);
         } catch {
-          return {
-            isError: true,
-            content: [
-              {
-                type: 'text',
-                text: `Error: File not found at path: ${filePath}`,
-              },
-            ],
-          };
+          return buildMcpToolErrorResponse([`Error: File not found at path: ${filePath}`]);
         }
 
         // Check if it's a directory
         const stats = await fs.stat(filePath);
         if (stats.isDirectory()) {
-          return {
-            isError: true,
-            content: [
-              {
-                type: 'text',
-                text: `Error: The specified path is a directory, not a file: ${filePath}. Use file_system_read_directory for directories.`,
-              },
-            ],
-          };
+          return buildMcpToolErrorResponse([
+            `Error: The specified path is a directory, not a file: ${filePath}. Use file_system_read_directory for directories.`,
+          ]);
         }
 
         // Read file content
@@ -79,40 +58,17 @@
 
         // If security check found issues, block the file
         if (securityCheckResult !== null) {
-          return {
-            isError: true,
-            content: [
-              {
-                type: 'text',
-                text: `Error: Security check failed. The file at ${filePath} may contain sensitive information.`,
-              },
-            ],
-          };
+          return buildMcpToolErrorResponse([
+            `Error: Security check failed. The file at ${filePath} may contain sensitive information.`,
+          ]);
         }
 
-        return {
-          content: [
-            {
-              type: 'text',
-              text: `Content of ${filePath}:`,
-            },
-            {
-              type: 'text',
-              text: fileContent,
-            },
-          ],
-        };
+        return buildMcpToolSuccessResponse([`Content of ${filePath}:`, fileContent]);
       } catch (error) {
         logger.error(`Error in file_system_read_file tool: ${error}`);
-        return {
-          isError: true,
-          content: [
-            {
-              type: 'text',
-              text: `Error reading file: ${error instanceof Error ? error.message : String(error)}`,
-            },
-          ],
-        };
+        return buildMcpToolErrorResponse([
+          `Error reading file: ${error instanceof Error ? error.message : String(error)}`,
+        ]);
       }
     },
   );

src/mcp/tools/grepRepomixOutputTool.ts

@@ -3,7 +3,7 @@
 import type { CallToolResult } from '@modelcontextprotocol/sdk/types.js';
 import { z } from 'zod';
 import { logger } from '../../shared/logger.js';
-import { getOutputFilePath } from './mcpToolRuntime.js';
+import { buildMcpToolErrorResponse, buildMcpToolSuccessResponse, getOutputFilePath } from './mcpToolRuntime.js';
 
 /**
  * Search options for grep functionality
@@ -83,29 +83,17 @@
 
         const filePath = getOutputFilePath(outputId);
         if (!filePath) {
-          return {
-            isError: true,
-            content: [
-              {
-                type: 'text',
-                text: `Error: Output file with ID ${outputId} not found. The output file may have been deleted or the ID is invalid.`,
-              },
-            ],
-          };
+          return buildMcpToolErrorResponse([
+            `Error: Output file with ID ${outputId} not found. The output file may have been deleted or the ID is invalid.`,
+          ]);
         }
 
         try {
           await fs.access(filePath);
         } catch (error) {
-          return {
-            isError: true,
-            content: [
-              {
-                type: 'text',
-                text: `Error: Output file does not exist at path: ${filePath}. The temporary file may have been cleaned up.`,
-              },
-            ],
-          };
+          return buildMcpToolErrorResponse([
+            `Error: Output file does not exist at path: ${filePath}. The temporary file may have been cleaned up.`,
+          ]);
         }
 
         const content = await fs.readFile(filePath, 'utf8');
@@ -125,51 +113,24 @@
             ignoreCase,
           });
         } catch (error) {
-          return {
-            isError: true,
-            content: [
-              {
-                type: 'text',
-                text: `Error: ${error instanceof Error ? error.message : String(error)}`,
-              },
-            ],
-          };
+          return buildMcpToolErrorResponse([`Error: ${error instanceof Error ? error.message : String(error)}`]);
         }
 
         if (searchResult.matches.length === 0) {
-          return {
-            content: [
-              {
-                type: 'text',
-                text: `No matches found for pattern "${pattern}" in Repomix output file (ID: ${outputId}).`,
-              },
-            ],
-          };
+          return buildMcpToolSuccessResponse([
+            `No matches found for pattern "${pattern}" in Repomix output file (ID: ${outputId}).`,
+          ]);
         }
 
-        return {
-          content: [
-            {
-              type: 'text',
-              text: `Found ${searchResult.matches.length} match(es) for pattern "${pattern}" in Repomix output file (ID: ${outputId}):`,
-            },
-            {
-              type: 'text',
-              text: searchResult.formattedOutput.join('\n'),
-            },
-          ],
-        };
+        return buildMcpToolSuccessResponse([
+          `Found ${searchResult.matches.length} match(es) for pattern "${pattern}" in Repomix output file (ID: ${outputId}):`,
+          searchResult.formattedOutput.join('\n'),
+        ]);
       } catch (error) {
         logger.error(`Error in grep_repomix_output: ${error}`);
-        return {
-          isError: true,
-          content: [
-            {
-              type: 'text',
-              text: `Error searching Repomix output: ${error instanceof Error ? error.message : String(error)}`,
-            },
-          ],
-        };
+        return buildMcpToolErrorResponse([
+          `Error searching Repomix output: ${error instanceof Error ? error.message : String(error)}`,
+        ]);
       }
     },
   );

src/mcp/tools/mcpToolRuntime.ts

@@ -190,3 +190,28 @@ export const formatToolError = (error: unknown): CallToolResult => {
     ],
   };
 };
+
+/**
+ * Creates a successful MCP tool response with type safety
+ */
+export const buildMcpToolSuccessResponse = (messages: string[]): CallToolResult => {
+  return {
+    content: messages.map((message) => ({
+      type: 'text' as const,
+      text: message,
+    })),
+  };
+};
+
+/**
+ * Creates an error MCP tool response with type safety
+ */
+export const buildMcpToolErrorResponse = (errorMessages: string[]): CallToolResult => {
+  return {
+    isError: true,
+    content: errorMessages.map((message) => ({
+      type: 'text' as const,
+      text: message,
+    })),
+  };
+};

src/mcp/tools/packCodebaseTool.ts

@@ -4,7 +4,12 @@ import type { CallToolResult } from '@modelcontextprotocol/sdk/types.js';
 import { z } from 'zod';
 import { runCli } from '../../cli/cliRun.js';
 import type { CliOptions } from '../../cli/types.js';
-import { createToolWorkspace, formatToolError, formatToolResponse } from './mcpToolRuntime.js';
+import {
+  buildMcpToolErrorResponse,
+  createToolWorkspace,
+  formatToolError,
+  formatToolResponse,
+} from './mcpToolRuntime.js';
 
 export const registerPackCodebaseTool = (mcpServer: McpServer) => {
   mcpServer.tool(
@@ -65,22 +70,7 @@ export const registerPackCodebaseTool = (mcpServer: McpServer) => {
 
         const result = await runCli(['.'], directory, cliOptions);
         if (!result) {
-          return {
-            isError: true,
-            content: [
-              {
-                type: 'text',
-                text: JSON.stringify(
-                  {
-                    success: false,
-                    error: 'Failed to return a result',
-                  },
-                  null,
-                  2,
-                ),
-              },
-            ],
-          };
+          return buildMcpToolErrorResponse(['Failed to return a result']);
         }
 
         // Extract metrics information from the pack result