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

Annotations already mark the operation read-only, idempotent, and non-destructive. The description adds useful behavioral detail by specifying the time granularity (annual and monthly) and the three irradiance output types, which goes beyond what the annotations provide.

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 sentences with no filler: the first delivers the resource and data content, and the second adds the intended use case. Every sentence earns its place.

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 read-only data lookup, the description covers what is returned, the granularity, and the practical context. It could be more complete by naming units or response shape, but none of the selection-critical information is 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%, with lat, lon, and address each already documented, including the either address OR lat+lon requirement. The description itself adds no parameter-level meaning, so the baseline 3 applies.

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 a specific resource: solar resource data for a location, and enumerates the exact irradiance metrics (DNI, GHI, latitude-tilt). It stops short of a 5 because it does not explicitly distinguish itself from the closely related nrel_pvwatts sibling or state a verb like 'retrieve'.

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 use case: 'site evaluation before sizing a solar system.' This tells an agent when the tool is relevant, but it doesn't explicitly discuss when to prefer nrel_pvwatts or another solar-related sibling.

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