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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered structurally. The description adds real behavioral guardrails beyond that — no product recommendations, no bill-savings promises — which tells the agent how to frame the answer, not just that it is a safe read.

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 short sentences, zero filler, with the primary use case stated before the exclusions. Every clause carries information an agent needs to select and frame the call.

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 single-optional-parameter, closed-world explainer with no output schema, the definition covers purpose, framing constraints, and exclusions, and the schema covers the privacy constraint. Minor gap: it does not say what the agent receives back (e.g. a public explainer page vs. a tailored answer), which the schema only hints at.

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?

There is a single optional parameter whose schema description already covers its purpose, emptiness semantics, and the sensitive-data exclusion at 100% coverage. The description contributes nothing about the parameter, which is acceptable given the schema does the work, but it adds no extra meaning.

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 names a specific resource (a home battery) and the specific content to be explained (what it stores, why backup is a separate feature), which is well beyond restating the name. It does not explicitly contrast with the sibling explainers (explain_solar, explain_hesl), so the boundary between this and adjacent topic pages is left implicit.

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 trigger ('use this when explaining...') plus two explicit exclusions: recommending a product and promising bill savings — those map onto siblings like product_faq and estimate_bill_savings. It stops short of naming those alternatives directly, so the routing is inferable rather than stated.

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