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

The annotations already establish readOnlyHint=true, openWorldHint=true, and destructiveHint=false. The description adds useful behavioral context beyond annotations: cost of 2 credits, ISO 8601 output format, and paid-plan gating for moon phase details and date selection.

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 short and front-loads the core purpose, output format, and cost. However, it redundantly repeats the tool name as 'Moonrise Moonset: Moonrise Moonset' before the actual sentence.

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?

For a simple two-required-parameter tool with an output schema and full schema coverage, the description is nearly complete. It covers cost and plan-gated features, though it does not address timezone behavior or whether the date parameter has default behavior.

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?

Schema description coverage is 100%, so the schema already documents lat, lon, and date. The description adds some context by noting date selection is tied to paid plans, but it does not add coordinate format or other semantic detail beyond the 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 states a specific verb and resource: calculates exact moonrise and moonset times for a geographic coordinate. It is clearly distinct from MoonPhases and MoonPosition by focusing on rise/set events, but it does not explicitly differentiate itself from those sibling tools.

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?

Usage is implied by the purpose and the cost/plan note, but the description does not state when to choose this tool over MoonPhases, MoonPosition, or SunriseSunset. No explicit exclusions or alternative-selection guidance are provided.

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