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

With no annotations, the description carries the full behavioral burden. It usefully discloses a per-call price of 0.001 USDC via x402, but does not itself explain the payment flow, rate limits, or return format; the payment flow is instead delegated to the schema.

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 two compact sentences: the first front-loads what the tool returns and its scope, and the second states the cost. There is no wasted or redundant text.

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 data-retrieval tool with complete schema coverage, the description covers the key outputs and pricing. Minor omissions remain around units, timezone handling, and return format, especially since there is no output schema.

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 parameters are already fully documented, including the paymentProof retry flow. The description adds only high-level place/date context, so the baseline of 3 is appropriate.

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 exactly what data is returned: sunrise, sunset, daylight duration, moon phase, and illumination, scoped to a place and date. It is clear and specific but does not differentiate itself from nearby siblings like weather or space_weather.

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 place-and-date framing implies when to use the tool, but there is no explicit when-to-use guidance, no named alternatives, and no exclusions. An agent can infer usage, but the description does not route it against competing tools.

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