The server defines 12 WhatsApp tools with reasonable naming and mostly complete schemas. All tools have descriptions (10 are 50+ chars), and parameters have types and descriptions. However, critical gaps exist: (1) No output schemas are documented, callers don't know what fields to expect from responses, forcing LLMs to guess. (2) No input validation or error recovery guidance, tools will fail silently or with generic errors. (3) No tool annotations (readOnlyHint/destructiveHint) to signal side effects to agents. (4) Pagination is incomplete, list_messages and list_chats have limit/page params but no total_count or next_cursor guidance. (5) No permission/scope documentation for sensitive write operations (send_message, send_file). The server is functional for basic read/write but lacks production-grade robustness.

• Document output schemas for all 12 tools in the tool registry. Specify all fields, types, and whether they are always present or optional. Example: send_message returns {success: bool, message_id: string, timestamp: ISO-8601, error?: string}.
• Add error recovery guidance to send_* and download_media descriptions. Example: 'If the recipient format is invalid, the error will specify the expected format (phone number or JID). If the file is not found, check the media_path. If the connection fails, retry after 5 seconds.'
• Implement confirmation step for send_message and send_file. Return {preview: string, requiresConfirmation: true} and accept a 'confirmed: bool' parameter. Or split into two tools: prepare_message (returns preview) + send_message (takes confirmed flag).
• Add tool annotations to tool registry. Mark send_message, send_file, send_audio_message with {destructiveHint: true}. Mark search_contacts, list_messages, list_chats, get_* with {readOnlyHint: true}.
• Enrich pagination. list_messages and list_chats should return {results: [...], total_count: int, page: int, limit: int, has_more: bool}. Document this in descriptions so LLMs know when to stop paginating.
• Formalize recipient parameter constraints. Define an enum or regex: recipient must match '^[0-9]+@(s|g)\.whatsapp\.net$' (JID) OR '^[0-9]{10,15}$' (phone). Add validation error: 'Invalid recipient. Provide phone number (10-15 digits) or JID (e.g., 1234567890@s.whatsapp.net)'.
• Document scope/permission requirements in tool descriptions. Example: 'send_message requires write:messages scope' and 'download_media requires read:media scope'. Define these in server capability metadata.