MCP Log Reader

Instructions

Implementation Reference

• src/index.ts:74-255 (handler)

  The complete handler implementation for the 'read_mcp_logs' tool. It handles parameter extraction, OS-specific log directory detection, file discovery using glob or fallback readdir, sorting by modification time, pagination, line filtering, tail reading, size limiting with truncation, error handling, and structured JSON-RPC response with pagination info.
  if (request.params.name === "read_mcp_logs") { const args = request.params.arguments || {}; const { lines = 100, filter = "", customPath, fileLimit = 5, // Limit number of files to process page = 1 // For pagination } = args as { lines?: number, filter?: string, customPath?: string, fileLimit?: number, page?: number }; try { // Get default log directory based on operating system let logDir: string; if (customPath) { logDir = customPath; } else { const homedir = os.homedir(); if (process.platform === 'darwin') { // macOS log path logDir = path.join(homedir, 'Library/Logs/Claude'); } else if (process.platform === 'win32') { // Windows log path logDir = path.join(homedir, 'AppData/Roaming/Claude/logs'); } else { // Linux/other OS log path (might need adjustment) logDir = path.join(homedir, '.config/Claude/logs'); } } await saveLog(`Looking for MCP logs in: ${logDir}`); let allLogFiles: string[] = []; try { // Use glob to find all mcp log files allLogFiles = await glob(`${logDir}/mcp*.log`); // If no files found, try a more general pattern as fallback if (allLogFiles.length === 0) { allLogFiles = await glob(`${logDir}/*.log`); } } catch (globError) { // If glob fails, try using readdir as a fallback const dirFiles = await readdir(logDir); allLogFiles = dirFiles .filter(file => file.startsWith('mcp') && file.endsWith('.log')) .map(file => path.join(logDir, file)); // If still no files, try any log file if (allLogFiles.length === 0) { allLogFiles = dirFiles .filter(file => file.endsWith('.log')) .map(file => path.join(logDir, file)); } } // Sort files by modification time (newest first) const filesWithStats = await Promise.all( allLogFiles.map(async (file) => { const stats = await fs.promises.stat(file); return { path: file, mtime: stats.mtime }; }) ); filesWithStats.sort((a, b) => b.mtime.getTime() - a.mtime.getTime()); // Paginate the files const totalFiles = filesWithStats.length; const startIndex = (page - 1) * fileLimit; const endIndex = Math.min(startIndex + fileLimit, totalFiles); // Get the files for the current page const logFiles = filesWithStats .slice(startIndex, endIndex) .map(file => file.path); if (logFiles.length === 0) { return { toolResult: { success: false, message: `No log files found in ${logDir}`, logDirectory: logDir } }; } const results: Record<string, string> = {}; // Process each log file - with size limiting const maxBytesPerFile = 100 * 1024; // 100KB per file max const maxTotalBytes = 500 * 1024; // 500KB total max let totalSize = 0; for (const logFile of logFiles) { try { // Check if we've already exceeded total max size if (totalSize >= maxTotalBytes) { const filename = path.basename(logFile); results[filename] = "[Log content skipped due to total size limits]"; continue; } const filename = path.basename(logFile); const content = await readFile(logFile, 'utf8'); // Split content into lines let logLines = content.split(/\r?\n/); // Apply filter if provided if (filter) { const filterLower = filter.toLowerCase(); logLines = logLines.filter(line => line.toLowerCase().includes(filterLower) ); } // Get the specified number of lines from the end const selectedLines = logLines.slice(-lines); const selectedContent = selectedLines.join('\n'); // Check if this file would exceed per-file limit if (Buffer.from(selectedContent).length > maxBytesPerFile) { // Take just enough lines to stay under the limit let truncatedContent = ''; let truncatedLines = []; for (let i = selectedLines.length - 1; i >= 0; i--) { const newLine = selectedLines[i] + '\n'; if (Buffer.from(newLine + truncatedContent).length <= maxBytesPerFile) { truncatedLines.unshift(selectedLines[i]); truncatedContent = truncatedLines.join('\n'); } else { break; } } results[filename] = '[Content truncated due to size limits]\n' + truncatedContent; totalSize += Buffer.from(results[filename]).length; } else { // Store the results if under limit results[filename] = selectedContent; totalSize += Buffer.from(selectedContent).length; } } catch (readError) { const errorMessage = readError instanceof Error ? readError.message : String(readError); results[path.basename(logFile)] = `Error reading log: ${errorMessage}`; totalSize += Buffer.from(results[path.basename(logFile)]).length; } } return { toolResult: { success: true, message: `Read logs from ${logFiles.length} file(s)`, logDirectory: logDir, logs: results, pagination: { currentPage: page, filesPerPage: fileLimit, totalFiles: totalFiles, totalPages: Math.ceil(totalFiles / fileLimit), hasNextPage: endIndex < totalFiles, hasPreviousPage: page > 1 } } }; } catch (error) { const errorMessage = error instanceof Error ? error.message : String(error); await saveLog(`Error reading MCP logs: ${errorMessage}`); throw new McpError(ErrorCode.InternalError, `Failed to read MCP logs: ${errorMessage}`); } }
• src/index.ts:43-67 (schema)

  Input schema defining the parameters for the read_mcp_logs tool: lines (tail count), filter (text search), customPath (override dir), fileLimit (files per page), page (pagination).
  inputSchema: { type: "object", properties: { lines: { type: "number", description: "Number of lines to read from the end of each log file (default: 100)" }, filter: { type: "string", description: "Optional text to filter log entries by (case-insensitive)" }, customPath: { type: "string", description: "Optional custom path to log directory (default is system-specific)" }, fileLimit: { type: "number", description: "Maximum number of files to read per page (default: 5)" }, page: { type: "number", description: "Page number for pagination (default: 1)" } } }
• src/index.ts:37-71 (registration)

  Registration of the 'read_mcp_logs' tool in the ListToolsRequestSchema response, including name, description, and reference to input schema.
  server.setRequestHandler(ListToolsRequestSchema, async () => { return { tools: [ { name: "read_mcp_logs", description: "Read MCP logs from the standard location", inputSchema: { type: "object", properties: { lines: { type: "number", description: "Number of lines to read from the end of each log file (default: 100)" }, filter: { type: "string", description: "Optional text to filter log entries by (case-insensitive)" }, customPath: { type: "string", description: "Optional custom path to log directory (default is system-specific)" }, fileLimit: { type: "number", description: "Maximum number of files to read per page (default: 5)" }, page: { type: "number", description: "Page number for pagination (default: 1)" } } } } ] }; });