9 tools with reasonable naming (verb_noun pattern) but critical gaps in schema completeness and parameter descriptions. Most tools lack explicit input schema validation in code. Descriptions are present but generic (avg ~100 chars, below 194-char baseline). Parameters documented in descriptions but not formally typed in visible schema definitions. No output schemas documented. Error handling minimal, no recovery guidance or actionable error messages. Security concerns: file operations lack path validation; no permission gates on destructive tools (feishu:access, feishu:send, feishu:upload-file).

• Document output schema for each tool. Example for feishu:list-messages: { messages: Array<{ messageId: string, senderId: string, content: string, timestamp: string }>, total: number, hasMore: boolean }
• Split feishu:access into 10 separate tools: set_dm_policy, add_user_to_allowlist, remove_user_from_allowlist, add_group_chat, remove_group_chat, set_mention_patterns, set_ack_reaction, approve_pairing_request, list_pending_pairings, list_access_config. Each tool does one thing.
• For feishu:send, use an enum or oneOf schema to enforce exactly one content type. Document: 'Provide exactly one of: text, richText, imageUrl, filePath, or card. Providing multiple will result in an error.'
• Add path validation to feishu:download-file: resolve the target path, verify it stays within INBOX_DIR, and reject symlinks. Use realpathSync() with try-catch to detect escape attempts.
• Wrap all tool implementations with consistent error handling: catch exceptions, classify as retryable/user-fixable/fatal, and return { success: false, error: string, suggestion?: string, retryable: boolean }. Example: 'User open_id not found. Try feishu:list-chats to see available users. Retryable: false.'