Two tools with minimal descriptions (both under 100 chars) and no documented output schemas. Tool names follow verb_noun convention (get_current_time, calculator) but descriptions lack context on WHEN to use each tool or WHAT they return. The calculator tool accepts a single string parameter with a description, but no input validation rules, error recovery guidance, or output format specification. No tool annotations (readOnlyHint, idempotentHint). Descriptions are in Japanese, which is acceptable but limits LLM reasoning in English-dominant systems. No error handling guidance beyond basic parse/eval failures.

• Add explicit output schema to both tools. E.g., get_current_time returns {"timestamp": "ISO 8601 string", "timezone": "string"}; calculator returns {"result": "number", "formula": "string"}.
• Expand descriptions to 80-150 chars with WHEN/WHY context. E.g., 'Get the current date and time in the server's local timezone. Use this when the user asks for the time or to timestamp events.'
• Document calculator's supported operators and constraints in the formula parameter description. E.g., 'Supports: +, -, *, /, ^, sum(), abs(), min(), max(). Max 500 chars. Returns error if formula is invalid.'
• Add actionable error messages. Instead of '計算式の解析に失敗しました', return 'Invalid formula: unsupported operator "@". Supported: +, -, *, /, ^, sum(), abs().'
• Add tool annotations via rmcp schema: mark both tools with readOnlyHint=true and idempotentHint=true to signal safety to LLMs.