Strong foundation with complete schemas and clear descriptions. All 7 tools have explicit input schemas with proper Zod validation, type definitions, and parameter descriptions. Tool names follow verb_noun convention (mail.read, mail.search, shop.orderStatus). Descriptions are concise (10-60 chars) and action-oriented. Output types are well-defined interfaces. However, descriptions are at the lower end of the 10-1024 char baseline (avg ~35 chars here vs 194 baseline), lacking context on WHEN to use each tool or dependencies between them. No error handling guidance, no recovery paths, and no output schema documentation in the tool registry itself. Security model is sound (no send path for mail, synthetic data only), but lacks explicit permission declarations and audit trail guidance.

• Expand tool descriptions to 50-200 chars, including WHEN to use and any prerequisites. E.g., 'Search mail threads by query. Use this to find relevant customer conversations before reading a full thread. Returns up to 50 results; use limit to control pagination.'
• Add output schema documentation to TOOL_REGISTRY entries. Create an 'output' field describing the return type structure, e.g., output: { type: 'object', properties: { threadId: { type: 'string' }, subject: { type: 'string' }, messages: { type: 'array' } } }
• Document error cases and recovery paths. E.g., 'If threadId not found, returns error 'THREAD_NOT_FOUND'. Try mail.search() with a partial subject to locate the correct thread.'
• Expand parameter descriptions to include format hints. E.g., 'Thread identifier (alphanumeric, 1-50 chars, e.g., thread-demo-1)' instead of just 'Thread identifier, minimum 1 character'.
• Adopt MCP standard tool annotations: add readOnlyHint: true to mail.read, mail.search, shop.* tools; add destructiveHint: false to mail.draft (since it's staged, not sent). Replace custom 'access' field with standard annotations.