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

Beyond the readOnlyHint/openWorldHint annotations, it discloses the data source, the daily-only freshness model, and a precise billing model ($0.002 USDC per successful call via x402, failures not charged). That is substantive context an agent needs before calling a paid endpoint; it does not discuss rate limits or result counts.

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?

Three tight sentences, front-loaded with the what and the field list, then limits, then price. The enumeration of return fields overlaps with the existing output schema, a small redundancy, but nothing is padded.

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 an output schema handling return values, annotations handling the read-only/open-world profile, and a single fully documented parameter, the description supplies everything else an agent needs: source, scope limits, and cost/failure billing.

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 the geo parameter is self-documenting, so the baseline is 3. The description adds real meaning by framing the parameter as a strict single-country scope and warning that no category dimension exists, which prevents misuse of geo for segmentation.

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 gives a specific verb+resource ('Today's trending Google searches for one country') plus the concrete payload (rank, query, approximate volume, backing news items). It is clearly distinct from siblings like news_radar or social_signal_aggregator by resource, but it never names or contrasts an alternative tool explicitly.

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 sets explicit boundaries on use: 'Country only', no industry categories, and 'daily trends, not a breakout history' – effectively telling the agent what this tool cannot answer. It stops short of naming which sibling to reach for when the user wants categories or historical breakout data.

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