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

Annotations already provide readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description reinforces these with 'read-only and idempotent' and adds operational detail: 'a live GET against the public IBGE Países API' and 'Returns Markdown.' This goes beyond the structured annotations and gives the agent concrete expectations about network dependency and output format.

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?

The description is well organized with a one-line summary, feature bullets, region list, code convention, examples, and a behavior note. Each section is short and non-redundant; no filler sentences are present.

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 tool with five optional parameters and an output schema, the description covers all operation modes, required code format, available regions, example invocations, and return format. The output schema handles return-value details. Nothing critical is missing for an agent to invoke it 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?

The input schema has 100% coverage, so the baseline is 3. The description adds value by providing worked examples that bind values to use cases (listar, detalhes, buscar, regiao) and enumerating the valid region strings. It supplements the schema without replacing it, which justifies a small uplift.

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 opens with 'Queries international country data via IBGE' and enumerates specific operations (list, details, search, filter by region). This clearly identifies the resource (international countries) and distinguishes it from sibling tools like ibge_estados and ibge_municipios, which focus on Brazilian geographic units.

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 provides concrete usage examples for each tipo value, lists valid regions, and specifies the ISO-ALPHA-2 code convention. It does not explicitly name alternative tools to use instead, but the 'international country data' framing and region list make the intended scope clear enough for an agent to decide when to use it.

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