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

Annotations already declare readOnly, idempotent, non-destructive and closed-world behaviour, so the safety profile is covered. The description adds genuinely non-obvious behaviour beyond that: results are grouped by country, one site per trade/country, the trade label is rendered in English unless a country is supplied, in which case the local trade word is returned.

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 compact sentences, front-loaded with what is listed and how it is grouped, followed by parameter behaviour. No filler; the only slightly cryptic phrase is 'Use the site in the other tools', which is terse rather than wasteful.

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 burden of describing returns and does so (grouping, site names, trade language). Combined with the fully covered input schema and read-only annotations, an agent has enough to invoke it correctly; only the relationship to the sibling tools stays underspecified.

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 already documents both parameters and their example values, so the baseline is 3. The description goes further by explaining the distinct result shape each parameter produces (single-country view vs. trade search), which the schema does not convey.

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 states a specific verb and resource ('Lists the sites'), plus a precise scope: one site per trade and country, grouped by country. It does not explicitly differentiate itself by name from siblings such as find_providers or get_service_info, but the resource and grouping behaviour are clear enough to select it correctly.

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 tells the agent how each optional parameter changes the result (country -> single country view with local trade word; trade -> search by trade), which implies usage but never states when this tool should be preferred over find_providers or get_service_info. 'Use the site in the other tools' hints at a downstream relationship without naming alternatives.

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