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

With readOnlyHint=true already signaling a safe read operation, the description adds useful behavioral context by revealing fuzzy name matching with the concrete example that 'Brasil' and 'Brazil' both resolve. It also summarizes the returned record fields. It does not contradict the annotations, though it does not discuss error or unknown-query behavior.

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 sentences carry all the essential information with no filler. The primary lookup modes are front-loaded, the return contents are summarized efficiently, and the fuzzy matching example adds value without bloating the description.

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 simple read-only lookup tool with a full input schema, output schema, and readOnlyHint annotation, the description is largely complete: it covers accepted inputs, result contents, and a notable matching behavior. The main gap is the lack of guidance around ambiguous or unknown queries and no sibling differentiation, but those are minor for this tool's simplicity.

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 the baseline is 3, but the description adds real meaning beyond the schema by explaining fuzzy matching behavior and giving concrete input examples for the query parameter. The 'by' parameter is left to the schema, which is acceptable given the schema already documents the auto/name/alpha2/alpha3 strategy.

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 clearly states a specific verb and resource: look up a country by name, ISO alpha-2, or alpha-3 code, and returns a full country record. It is understandable on its own, but it does not explicitly distinguish itself from the sibling ref_geo_search, so it stops short of full sibling differentiation.

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 implies when to use the tool: when you have a country identifier and want the full country record, including fuzzy name matches. However, it gives no explicit guidance about when not to use it or what distinguishes it from ref_geo_search and other lookup tools, so usage context remains implicit rather than explicit.

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