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

Annotations already declare readOnly, idempotent and non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond them: 'right now' recency and the 'most countries first' result ordering, neither of which appears in the schema. It says nothing about auth, rate limits, or result size, so it lands at a solid 3 rather than higher.

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?

A single front-loaded sentence with no filler. The scope constraint and the output ordering both earn their place, and there is nothing an agent must read past to get the core behavior.

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 two-parameter read-only tool with no output schema and no nesting, the description covers the result ordering and the country threshold but omits what 'limit' controls and what the returned items look like (topic, count, country list?). Adequate but with visible gaps for an agent that must interpret the response.

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 0%, so the description must compensate. It clarifies the meaning of minCountries by stating the '2+ of the 30 countries' universe and implicitly explains the lower bound seen in the schema, but it never explains the 'limit' parameter or its units. Half the parameters are left to inference, which caps this at a mid score.

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 resource ('topics trending right now') and scope ('in 2+ of the 30 countries'), which distinguishes it from single-location siblings like trending_now or trending_day. It does not name those siblings explicitly, so an agent gets the gist but no direct routing hint.

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?

Usage is implied by the cross-country framing plus the 'right now' recency, which suggests this is the multi-country real-time trending tool. There is no explicit when-to-use statement, no mention of when trending_now or trending_day is preferable, and no prerequisites.

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