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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower. The description adds genuine extra context: it is reference-only material, the children's figure is a daily average, and WHO sets no quantified sedentary-behaviour threshold — data nuances the annotations cannot convey.

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?

Labelled Purpose/Guidelines/Limits structure is front-loaded and scannable, with no filler prose. The trailing 'Ex: query_activity_guidelines()' adds little since the tool takes no required arguments, but it is brief.

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?

An output schema exists, so return values need not be described, and annotations cover the safety profile. Combined with the population-group scope and the reference-only caveat, an agent has what it needs to select and call this correctly.

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% with five self-documented parameters (limit, offset, keyword, language, response_format), so the schema carries the burden. The description adds nothing about paging, filtering, or language/format selection, so baseline 3 applies.

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 (physical activity guidelines) and enumerates the population groups covered (adults, children, older adults, pregnancy). It is clearly distinguishable from adjacent health siblings such as get_dietary_guidelines and query_health_myths, though it never names or contrasts them 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?

The 'Guidelines: use for activity-volume questions' line gives explicit usage context, and the 'Limits' line rules out individual/personalized advice. It stops short of naming an alternative tool or when NOT to call it beyond the advice boundary.

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