This server registers 8 tools with explicit schemas and descriptions visible in src/index.ts. All tools follow verb_noun naming convention (list_emails, search_emails, send_email, modify_email, list_events, create_event, update_event, delete_event). Descriptions are present and substantive (most 30-80 chars, adequate for tool selection). Input schemas are fully specified with type definitions and parameter descriptions. However, there are critical gaps: (1) Output schemas are NOT documented anywhere, the code does not declare what each tool returns, forcing LLMs to guess at response structure; (2) Error handling is minimal, no recovery guidance, no error classification, no actionable error messages; (3) No support for idempotency hints or destructive operation safeguards (e.g., delete_event has no confirmation step despite being destructive); (4) Parameters could be more constrained (e.g., email tools accept free-form 'query' strings with no validation hints beyond examples); (5) OAuth credentials are injected via environment variables (good pattern), but there is no audit logging, permission checks, or scope declarations. The server is functional but lacks production-grade error handling and output documentation.

• Document output schemas for all tools. For example, list_emails should declare: { emails: [ { id: string, from: string, subject: string, snippet: string, timestamp: string } ], totalResults: number }. This allows LLMs to extract and chain data without guessing.
• Add a confirmation_required flag or dry-run mode to delete_event. Return a token that the LLM must pass back to confirm deletion, preventing accidental data loss.
• Implement input validation with actionable error messages. For search_emails, validate the query against Gmail's query syntax and return: 'Invalid Gmail query. Did you mean "from:user@example.com"? Valid operators: from:, to:, subject:, has:attachment, is:unread, after:, before:, label:'. This guides LLMs to self-correct.
• Add an 'X-Idempotency-Key' pattern: send_email and create_event should accept an optional idempotency_key parameter. Return a structured response with the resource ID and a flag indicating if it was newly created or a duplicate (201 vs 200).
• Implement pagination: list_emails and list_events should return { items: [...], totalCount: number, nextToken?: string }. If results exceed maxResults, include nextToken so the LLM can fetch subsequent pages.
• Add permission checks: wrap each tool with a scope check. E.g., send_email requires scopes [gmail.send]; delete_event requires [calendar.events]. Return a clear error if the agent lacks required scopes: 'Insufficient permissions. This agent can: read:email, read:calendar. Required: send:email.'
• Add audit logging: log each tool call with { timestamp, tool_name, parameters (sanitized), result, error } to stderr or a logging service. This enables compliance and debugging.