Two tools with minimal documentation. send_message has a basic description (67 chars) and input schema with type strings and descriptions, but lacks output schema documentation and error guidance. list_contacts has a trivial description (43 chars) and no parameters. Neither tool declares what happens on failure, how to retry, or what fields the response contains. No tool annotations (readOnlyHint, destructiveHint, idempotentHint). Descriptions are below the 194-char baseline for production tools. No pagination support despite list_contacts returning arrays. send_message is a WRITE operation with no confirmation or dry-run pattern.

• Add explicit output schema documentation for send_message. Document the WAHA response structure (e.g., {"success": boolean, "messageId": string, "timestamp": string}).
• Add destructiveHint annotation to send_message and update description to state: 'Sends an irreversible WhatsApp message. This action cannot be undone.'
• Enhance send_message error handling to return actionable messages: catch httpx.HTTPStatusError and return '{"error": "Invalid phone number. Use international format: +5511999887766"}' instead of raising.
• Expand list_contacts description to 100+ chars: 'Returns all pre-loaded WhatsApp contacts. Call this first to discover available recipients before sending messages. Returns array of {name, number} objects.'
• Add limit and offset parameters to list_contacts to support pagination and prevent context bloat on large contact lists.