18 tools with complete input schemas and descriptions in Russian. However, descriptions are generic and lack LLM-optimization guidance (e.g., 'when to use', 'prerequisites', 'what it returns'). Most descriptions are 50-150 chars, below the 194-char baseline for A+ tools. Parameters lack type constraints (no enums for folder names, no min/max for limits). No output schemas documented. Error handling is absent, no recovery guidance, no actionable error messages. Tool composition is reasonable (single responsibility), but missing critical chaining metadata (e.g., search-emails returns UIDs but read-email expects UID, this works, but not explicitly documented). Destructive tools (delete-email, send-draft) lack confirmation patterns. No tool annotations (readOnlyHint, destructiveHint, idempotentHint) despite clear risk levels.

• Add output schemas to every tool. Document the structure of responses (e.g., list-folders returns [{name, delimiter, flags}, ...]; check-inbox returns {emails: [{uid, from, subject, date, size, flags}, ...], total_count}). This enables LLMs to chain tools correctly.
• Expand descriptions to 150 - 250 chars. Include 'when to use' and 'what it returns'. Example: 'Search emails by sender, recipient, subject, date range, or flags. Returns a list of UIDs, pass these to read-email to fetch full content. Useful for filtering before reading.'
• Add enum constraints for 'folder' parameter across all tools. Define valid folders (INBOX, Drafts, Sent, Trash, custom folder names) and document the format. Reject invalid folder names with actionable errors.
• Add min/max constraints for numeric parameters. 'limit' should be 1 - 100 (default 20). Document that 'since' and 'before' require YYYY-MM-DD format and validate server-side with clear error messages.
• Implement tool annotations in the MCP response. Mark delete-email and send-draft with destructiveHint=true. Mark read-email, check-inbox, search-emails, list-folders, get-attachment with readOnlyHint=true. Mark idempotent operations (mark-as-read, flag-email) with idempotentHint=true. This enables client-side safety guardrails.