Single tool with adequate naming and schema but weak description quality. The 'moonphase' tool has a clear verb-noun structure and properly defined input schema with type information. However, the description lacks detail about when to use the tool, what it returns, and operational context. The parameter description states it's 'optional' but the code actually defaults to current time silently, this dependency is not clearly documented. No output schema is documented for the LLM, forcing it to infer the response structure. The tool is read-only and simple, which helps, but does not meet production baseline for descriptions (194 chars average; this one is only 67 chars).

• Expand tool description to 150 - 200 chars: 'Calculate the moon phase (age in days and illumination percentage) for a given date in RFC3339 format. If no date is provided, uses the current UTC time. Returns age (0 - 29.53 days) and illumination (0 - 100%).'
• Document the output schema explicitly in the tool definition or server documentation: 'Returns {age: float (0 - 29.53 days), illumination: int (0 - 100%)}.'
• Update parameter description: 'datetime: ISO 8601 / RFC3339 format string (e.g., 2025-01-15T10:30:00Z). Optional; if omitted, uses current UTC time.'
• Add error handling guidance: when datetime parsing fails, return 'Invalid datetime format. Use RFC3339 format (e.g., 2025-01-15T10:30:00Z).' Current code does this correctly, but should be documented in the tool description.
• Consider adding a 'date_only' parameter as an alternative to requiring full RFC3339, reducing LLM formatting burden for simple date queries.