MCPcube defines 22 tools with consistent naming (verb_noun pattern) and reasonable descriptions (avg ~100 chars). All tools have input schemas with typed parameters and descriptions. However, output schemas are not documented, LLMs cannot predict response structure. Error handling is minimal; no recovery guidance or actionable error messages visible. Destructive operations (deleteFolder, deleteContact, deleteIdentity) implement a two-step confirmation pattern, which is good, but lack explicit dry-run or rollback guidance. Security posture is strong (token hashing, AES-256-GCM encryption in schema), but no tool-level permission declarations or audit trail documentation. Composition is sound, tools are single-responsibility and chainable (e.g., listMessages → getMessage → sendMessage). Parameter defaults are conservative (folder='INBOX', limit=50-100), reducing accidental misuse.

• Document output schemas for all tools. For paginated results (listMessages, listContacts, listIdentities, searchMessages), include total_count, limit, offset, and next_cursor fields in the documented response.
• Add error classification to tool descriptions. E.g., 'Returns 404 if folder not found (user-fixable: check folder name). Returns 500 on IMAP connection failure (retryable: wait and retry).'
• Declare required scopes for each tool. Add a 'scopes' field to tool metadata: sendMessage requires ['write:email'], deleteContact requires ['write:contacts', 'delete:contacts'].
• Standardize OAuth tool names to camelCase: rename device_authorize → deviceAuthorize, device_token → deviceToken. Align with verb_noun pattern.
• Define schema for 'fields' parameter in updateContact and updateIdentity. Use an object schema with properties: {name, firstname, surname, organization, email, phone, notes}, each with type and description.