Proton MCP has 35 tools with consistent naming (verb_noun pattern) and basic descriptions. However, critical gaps undermine quality: (1) Output schemas are completely undocumented, no tool declares what fields it returns, forcing LLMs to guess at response structure. (2) Many parameter descriptions are minimal (10-30 chars) and lack constraints, ranges, or format guidance. (3) No error handling guidance, tools return raw JSON errors without recovery hints. (4) Sensitive operations (delete_message, delete_event, trash_item) lack confirmation/dry-run patterns. (5) Tool composition issues: mail__send_message and mail__reply_message both accept attachments but with slightly different schemas; no pagination on list tools despite potentially large result sets. Naming is solid (mail__*, pass__*, drive__*, calendar__*), but descriptions average ~80 chars, below the 194-char baseline for A+ tools. Schema validation is present (Zod) but output documentation is absent.

• Document output schemas for all 35 tools. For each, specify: field names, types (string|number|boolean|object|array), and what each field represents. E.g., mail__list_messages should return {messages: [{id, from, subject, date, preview}], total_count}.
• Add pagination to list tools: mail__list_messages, mail__list_messages_in_folder, calendar__list_events, pass__list_items, drive__list_files. Include limit (1-50, default 20), offset/cursor, and total_count in responses.
• Enhance parameter descriptions with constraints and examples. E.g., mail__move_message folder param: 'Destination folder name. Valid values: INBOX, Sent, Drafts, Archive, or custom label names (use mail__list_folders to discover).'
• Implement confirmation pattern for destructive tools. Add optional 'dry_run' parameter to mail__delete_message, drive__delete, calendar__delete_event. Return what would be deleted without executing.
• Wrap error responses with recovery guidance. Instead of {error: 'Connection failed'}, return {error: 'IMAP connection failed', retryable: true, hint: 'Check Proton Bridge is running on 127.0.0.1:1143'}.