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

Beyond the readOnly and openWorld annotations, the description discloses the data source and license, the time format and offset behavior, the default date, and precise billing details: $0.002 USDC per successful x402 call and no charge for failures. This gives the agent important operational context before invocation.

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 compact and front-loaded with what the tool returns, followed by necessary time-format, attribution, and pricing notes. Every sentence adds useful information without repetition.

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 output schema exists and the input schema is fully documented, the description supplies the remaining context an agent needs: data source, timezone offset behavior, default date, and billing model. Nothing material for correct invocation appears to be missing.

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 lat, lon, and date are already well documented. The description repeats the coordinate/date framing and default-today behavior but adds no new parameter-level syntax or constraints 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 names a specific resource and the exact outputs: sunrise, sunset, solar noon, day length, moonrise, moonset, and phase for a coordinate and date. This clearly distinguishes it from weather, tides, timezone, and date_calc siblings by focusing on solar and lunar astronomical 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?

It states the core usage context, a coordinate and date with today as default, which implies when the tool is appropriate. However, it does not explicitly say when to use this instead of weather, tides, timezone, or date_calc, nor does it provide exclusions or alternatives.

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