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

Annotations already establish readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds useful output context (cost, payback timeline, incentive guidance) that the annotations do not convey, though it says nothing about precision, assumptions, or regional limitation of the results.

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, zero filler, with the trigger front-loaded and the return payload second. Every clause 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?

With no output schema, the description correctly covers the return payload, and annotations cover safety. What remains thin is the assumption surface (e.g., regional pricing, whether incentives are location-specific), a minor gap for a four-parameter estimator.

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% and each of the four parameters (including three enums) is documented in the schema itself. The description adds no syntax, units, or interpretation beyond that, 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?

States a specific domain (solar) plus the calculations performed (system cost, payback timeline, incentive guidance), and the name itself separates it from the sibling cost calculators. It never explicitly names a sibling, so 4 rather than 5.

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 opening clause gives an explicit trigger ('Use when a user asks what solar panels cost, solar installation cost, or solar payback period'), which maps directly onto user intent. It offers no when-not conditions or routing to the electrical/HVAC/roofing calculators, so it stops short of 5.

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