chuk-mcp-celestial

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries full burden and does an excellent job disclosing behavioral traits. It explains the return format (MoonPhasesResponse with phasedata list), time format (UT1, not local time), lunar cycle duration (29.5 days), and practical applications. The only minor gap is it doesn't mention error handling or rate limits, but otherwise provides comprehensive behavioral context.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is well-structured and appropriately sized. It starts with the core purpose, then provides usage context, followed by detailed parameter documentation, return format, practical tips, and a complete example. Every section adds value with zero redundant information, and the information is front-loaded with the most important details first.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity (2 parameters, no output schema, no annotations), the description provides complete context. It covers purpose, usage guidelines, parameter details, return format, time zone considerations, lunar cycle context, practical applications, and includes a working example. No additional information is needed for effective tool use.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 0% schema description coverage, the description fully compensates by providing detailed parameter semantics. It explains the date format (YYYY-MM-DD, no leading zeros required), valid range (1700-01-01 to 2100-12-31), num_phases range (1-99), default value (12), and relationship to lunar cycles (12 phases = 3 complete cycles, each cycle has 4 phases). This adds significant value beyond the bare schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'Get upcoming moon phases starting from a given date' with specific details about what it returns (next N moon phase occurrences with exact times). It distinguishes from siblings by focusing specifically on moon phases rather than earth seasons, planet events, solar eclipses, or general sky/sun-moon data.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides explicit guidance on when to use this tool: 'Useful for planning astronomical observations, photography, or understanding lunar cycles.' It also includes a 'Tips for LLMs' section with specific use cases (astronomy, photography, fishing/hunting, gardening) and alternative parameter values for different timeframes (num_phases=4 for next month, 12 for next quarter, 48 for next year).

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.