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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint. Description adds local computation detail and explains output fields, but does not cover potential limits or side effects. Useful extra context beyond annotations.

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?

Two concise paragraphs: first listing outputs, second providing tide context and computation note. No fluff, front-loaded with essential information. Every sentence adds value.

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?

Covers purpose, output fields, optional parameters (date, end_date, lat/lon, format), and context (tides, local computation). No missing pieces for a read-only retrieval tool with five optional inputs.

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?

All five parameters have schema descriptions (100% coverage). The tool description adds meaning by explaining what the tool returns (phase name, illuminated fraction, etc.), complementing the schema without redundancy. Adds value beyond baseline.

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?

Clearly states the tool retrieves moon phase data for a date or date range, listing specific output fields (phase name, illuminated fraction, age, distance, diameter, waxing/waning). Distinguishes from sibling tools like astro_get_next_moon_phase which focuses on upcoming phases.

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?

Explicitly mentions tide context (spring/neap tides) and notes 'Computed locally — no NOAA data involved,' guiding users away from NOAA siblings when local computation is acceptable. Provides clear when-to-use context.

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