The server defines 9 tools with complete naming following verb_noun convention, but exhibits significant gaps in parameter descriptions, output schema documentation, and error handling. Tool names are clear and action-oriented (read_emails, send_email, search_emails, etc.), but parameter descriptions are inconsistent, some parameters like 'message_ids' in mark_as_read and add_labels lack detailed format guidance. No output schemas are documented for any tool, forcing LLMs to infer result structure. Error handling is absent from the provided code; no recovery guidance or error categorization visible. The server follows the MCP SDK patterns but lacks polish in descriptions and schema completeness expected of production-grade agents tools.

• Document the return type for every tool. Example for read_emails: 'Returns an array of EmailMessage objects, each containing {id, threadId, from, to, subject, date, snippet, body (if requested), labels}. Limited to max_results items.'
• Add actionable error messages with recovery hints. Example: 'If Gmail API returns 401 (Unauthorized), token may be expired, call get_auth_url() to refresh. If 404 (message not found), the email may have been deleted, use search_emails() to verify.'
• Expand parameter descriptions with format details. For message_ids: 'Array of Gmail message IDs (string format, e.g. ["18c1234567890abcdef", "18d0987654321fedcba"]). Obtain IDs from read_emails or search_emails results.'
• Add pagination support: include 'next_page_token' or 'offset' in read_emails/search_emails outputs; accept 'page_token' or 'offset' as optional input params to enable iterating large result sets.
• Implement a confirm_send_email tool or optional 'confirm: true' parameter to support a dry-run + confirmation workflow before sending irreversible emails.
• Clarify idempotency contract: document whether mark_as_read(same_message_ids) called twice is safe; document whether send_email with identical parameters creates duplicates or reuses.
• Expand get_labels description: 'Fetches all custom and system labels available in the Gmail account. Returns an array of {id, name, type (system/user)} objects. Use label names/IDs with add_labels() and search_emails() filters.'
• Add error classification to function docstrings: mark send_email as 'DESTRUCTIVE, this action is irreversible; include confirmation step' and mark read_emails as 'SAFE, read-only, always idempotent'.