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

The annotations already establish read-only and open-world behavior, so the description need not repeat safety details. It adds useful context that the result matches sun_hours and that the tool operates on WGS84 points in mainland Norway, but it does not describe the return shape, units, or computation details beyond the sibling equivalence.

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 definition is a single front-loaded sentence with no wasted wording. The sibling reference, coordinate system, geographic scope, and target use are all packed efficiently.

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 three-parameter variant with no output schema, the description supplies the key selection and scoping context. It delegates output semantics to sun_hours and leaves some invocation details to the schema, which is acceptable given the schema's bounds and language description.

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 coverage is low at 33%, so the description must help interpret lat/lon. It does so by specifying WGS84 and mainland Norway scope, which meaningfully clarifies the required coordinates, but it does not mention the lang parameter or add syntax beyond the schema's bounds and enum.

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 identifies this as the coordinate-based variant of sun_hours, scoped to a WGS84 point in mainland Norway. It clearly distinguishes from the address-based sibling by targeting cabins or plots without street addresses, though it relies on 'same as sun_hours' rather than directly stating the computed result.

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 gives a clear usage condition: use this for a cabin or plot without a street address, which implicitly routes address-based queries to sun_hours. It does not explicitly state exclusions or when not to use it, but the alternative is clear from the sibling reference.

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