This Gmail MCP server has multiple critical gaps in definition quality. While tool naming follows verb-noun conventions and schemas are visible in main.go, descriptions are present but generic, parameter coverage is incomplete, and output schemas are entirely undocumented. Critically, there is no visible error handling guidance, no confirmation mechanisms for destructive operations (send_draft, create_draft), and no documentation of what these tools return. The server lacks schema documentation for outputs, meaning LLMs cannot plan downstream operations or extract structured data reliably. Parameter descriptions exist but lack specificity around formats, ranges, and validation rules. For example, 'search_threads' accepts a 'query' parameter described only as 'Gmail search query string' without explaining what syntax is valid or what the response contains. The 'analyze_thread' tool delegates to OpenAI but provides no documentation about the analysis_type enum values or what output to expect. Overall, this reads as a functional prototype rather than a production-grade tool definition.

• ADD OUTPUT SCHEMAS. For each tool, document the return type structure (JSON object with typed fields). Example for search_threads: 'Returns: {threads: [{thread_id: string, subject: string, preview: string, message_count: int, timestamp: ISO-8601}], total_count: int, has_more: boolean}'
• EXPAND DESCRIPTIONS TO 100-200 CHARS. Include WHEN to use each tool and what it returns. E.g., send_draft should say: 'Send a previously created draft to recipients. This is IRREVERSIBLE, the message will be sent immediately. If you need user approval first, call create_draft and get_thread_drafts for review.'
• FORMALIZE PARAMETER ENUMS. Convert 'output_format' (base64|text|markdown) and 'analysis_type' (summary|sentiment|action_items|key_points) to JSON Schema enums. Add validation: 'analysis_type must be one of: summary, sentiment, action_items, key_points.'
• ADD NUMERIC BOUNDS. Set max_results to 1-100 with default 10. Document reasonable limits for each parameter.
• DOCUMENT PAGINATION. search_threads should state: 'Returns paginated results. Use max_results (1-100) to limit per call. Response includes has_more: boolean and next_cursor: string (if applicable) to fetch additional pages.'
• ADD ERROR GUIDANCE. Each tool should document common errors and recovery paths. Example for send_draft: 'If Draft not found, verify draft_id with get_thread_drafts(). If sending fails due to invalid recipient, check email format in to field.'
• ADD CONFIRMATION STEP FOR send_draft. Implement a dry-run parameter or separate confirm_send_draft tool so agents can show drafts to users before sending.