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

Annotations cover the safety profile (readOnlyHint, idempotentHint, openWorldHint), and the description adds substantial context the annotations cannot: the credit cost model (1 credit for a new analysis, free estimate-only, 1 credit to open a building not opened in a year), all four `status` semantics, the ~20s running duration with repeat-request deduplication, and the `basis`/`planesAreAssumed`/`roofSurvey` fallback semantics. This is exactly the extra behavioral detail an agent needs before invoking a metered tool.

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?

Information is front-loaded: purpose and return shape come first, then usage questions, then cost/status nuance. The status enumeration and basis clauses are long run-on sentences, but each clause carries real operational meaning, so the length is largely earned rather than padding.

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 and a single parameter, the description carries the full burden and meets it: it names the returned plane fields, the panel/capacity/yield figures, and the discriminator fields (`status`, `basis`, `planesAreAssumed`, `roofSurvey`). Nothing an agent needs to call this correctly or interpret the response 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 coverage is 100% and there is only one parameter, so the baseline is 3. The description adds meaning beyond the schema by specifying where the value comes from ('by the buildingId an earlier result gave'), which helps an agent that has not retained the id know to pull it from a prior call.

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 verb and resource ('reads one building's roof from imagery') and enumerates exactly what comes back (planes with facing, pitch, area, sunshine, panels; capacity and yield). It also distinguishes itself from siblings by noting that 'search results already carry stored solar figures', which tells the agent when the roof tool is the wrong one.

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?

Gives explicit when-to-use context with sample user questions ('what is the roof like?', 'how many panels fit?', 'which way do the roof planes face?') and the exclusion 'one building per request; search results already carry stored solar figures'. The condition selecting this tool over search/find siblings is unambiguous.

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