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

Annotations already establish readOnly/idempotent/non-destructive/openWorld semantics, so the burden is lighter. The description still adds genuine behavioral context the annotations don't: the 30-day lookback bound, the 1-5 country cap, ordering ('biggest first'), and the returned fields (first/last seen, peak traffic, news).

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?

One dense, front-loaded sentence with a scope-first structure ('Every trending search seen on one UTC day...'). Nothing is wasted, though the trailing clause stack ('with first/last seen, peak traffic and news') makes it a bit run-on.

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 carries the return-shape burden and does so by enumerating the fields returned. Missing coverage of the limit and minTraffic parameters keeps it from being fully complete for a 4-parameter tool.

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 only 25% (geo, limit, minTraffic are undocumented in the schema), so the description must compensate. It does add real meaning for geo ('1-5 countries') and date ('today or last 30 days', 'one UTC day'), but says nothing about limit or minTraffic, leaving half the parameters ambiguous — partial compensation, not full.

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 (trended), resource (trending searches), and precise scope (one UTC day, 1-5 countries). It is clear what the tool returns, though it never names a sibling like trending_now to make the day-vs-live distinction explicit.

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 description implies usage via the date window ('today or the last 30 days'), which tells the agent this tool covers historical days, unlike the live sibling trending_now. However, there is no explicit when-to-use/when-not or any routing to cross_country_trends or topic_history, so the agent must infer the choice.

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