Critical gaps across all dimensions. Tool descriptions are present but minimal (avg 80 chars, well below 194-char baseline). Parameter descriptions are entirely missing (null values visible in schema). No input validation, error handling guidance, or output schema documentation. The 'add' tool lacks any description. Security concerns: hardcoded credentials in auth.ts (access_token, client_id, client_secret visible in source). No pagination support despite email filtering. Tool composition is reasonable (5 distinct tools), but parameter naming lacks clarity (e.g., 'maxresult' should be 'max_results'; 'id' should be 'email_id'). Schemas use Zod but descriptions are null throughout.

• Add non-empty descriptions to all 5 parameters across all tools. Format: 'The [parameter name] that controls [what it does]. Valid values: [enum or range]. Example: [realistic example].' Target 50 - 150 chars per param.
• Move credentials to environment variables or a secure vault. Replace hardcoded access_token, client_id, client_secret in auth.ts with process.env.GMAIL_ACCESS_TOKEN, etc. Never commit secrets to source.
• Document output schemas for each tool. E.g., add_response: {type: 'object', properties: {result: {type: 'number'}, error: {type: 'string|null'}}}. Return structured JSON, not plain text.
• Add error handling with recovery hints. E.g., 'Failed to send email: recipient invalid. Verify email format ([email protected]) and try again.' Include actionable next steps.
• Rename parameters for clarity: 'maxresult' → 'max_results'; 'id' → 'email_id'; 'from' → 'sender_email' (since description says it's always the same). Use verb_noun naming for tools: 'send_a_email' → 'send_email'.