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 context beyond that: it is owner-gate exempt because only public cohort data is used, and it returns a percentile framed as 'scores better than X% of peers'.

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 tight sentences with no filler, front-loading the action and corpus before the input/output contract and the access note. Every clause carries information an agent can act 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 supplies the essential return semantics (a cohort percentile) and the input provenance, which is enough to call the tool correctly. It would be stronger if it resolved whether sector actually affects the cohort today, since that ambiguity is the main remaining gap.

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%, so all five parameters are already documented, and the description mostly restates cohort selection that the schema covers. It does add slight meaning by noting the score originates from scan_domain, but it also calls sector a usable optional filter while the schema says sector filtering is only planned for a future release — a mildly misleading mismatch.

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 and resource ('Rank a domain against its country or global cohort') plus the corpus used (GSI benchmark) and the output shape (a percentile). It does not explicitly contrast itself with the close sibling get_benchmark, so sibling differentiation relies on the reader inferring that this is the per-domain ranking tool.

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 ties usage to a clear workflow by saying the score comes 'from scan_domain', which tells an agent when this tool applies (after a scan). It does not state exclusions or name an alternative such as get_benchmark, so the agent gets context but not routing rules.

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