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

Annotations already establish read-only, idempotent, non-destructive behavior. The description adds valuable context: the data comes from the world-countries dataset with no rate limits, plus latest World Bank figures, and the tool is free. This tells the agent about data provenance, freshness, and operational constraints beyond the annotations.

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 compact and front-loaded, leading with the full list of returned attributes before briefly noting data sources, rate limits, and pricing. Every sentence adds useful information with no filler or redundancy.

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 single-parameter read-only lookup with comprehensive annotations and no output schema, the description is complete: it enumerates the response fields, states data sources and limitations, and clarifies the tool is free. An agent has enough context to decide whether and how to invoke it.

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 already describes the single parameter as "name or ISO code" with 100% schema description coverage, so the baseline is 3. The description does not add further parameter-specific details such as accepted formats or examples, but it does imply the country must be a valid country name or ISO code through the phrase "Any country's essentials."

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 identifies the tool as returning comprehensive country facts, listing specific fields such as capital, population, GDP, currencies, languages, calling code, TLD, time zones, driving side, borders, and flag. This makes the tool's function explicit and distinguishes it from any sibling tool, none of which are country fact lookups.

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 "Any country's essentials" provides a clear use case: fetch broad static and economic facts for any country. It implies when this tool should be chosen, though it does not explicitly state when not to use it or name alternative tools. Given the sibling list contains no comparable country-facts tool, this is adequate.

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