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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds a real behavioral trait beyond them: the default filter hides unsupported countries, which an agent could otherwise wrongly assume were included. It does not cover response shape or any rate-limit behavior, keeping it short of a 5.

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 terse fragments, front-loaded with the resource and its return fields, with the default-filter caveat second. Nothing is padded, though the 'GET /countries' clause is only marginally useful to an agent that never sees transport details.

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 parenthetical field enumeration carries the return-value information an agent needs, and the default-filter note covers the only parameter. For a simple single-parameter read tool this is close to complete; only explicit sibling routing is absent.

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 the single parameter include_unsupported is already documented with its default. The description's 'By default only supported countries' reinforces that default but adds no syntax or format detail beyond the schema, so the 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?

A specific verb+resource (list shipping countries) with the returned fields enumerated in parentheses, so an agent knows exactly what comes back. It is distinguishable from siblings like gooten_list_currencies by the field list, though the description never names those siblings 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 phrase 'By default only supported countries' implies when the default listing is appropriate, but there is no explicit routing to alternatives such as gooten_validate_address or gooten_get_shipping_options, and no stated exclusions. Usage is inferable rather than spelled out.

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