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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds real behavioral context beyond that: data provenance (static dataset + World Bank), that there are no rate limits, that the tool is free, and that errors return isError with a message and are not charged. Return format is covered by the output schema.

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?

Front-loads the value proposition (the field list), then provenance, then price and error semantics. Dense but every clause carries information; only the 'Price: free' note is marginal given no pricing annotation exists to contradict it.

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?

Covers source data, freshness (latest World Bank figures), cost, and error behavior, while the output schema handles return values. For a single-parameter lookup tool this leaves nothing an agent needs missing.

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?

One parameter at 100% schema coverage, and the description's 'name or ISO code' phrasing merely restates the schema's own description. No additional syntax examples (e.g. 'US' vs 'United States' vs 'USA') are provided, 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?

States a specific resource and enumerates the exact fields returned (capital, population, GDP, currencies, languages, calling code, TLD, time zones, driving side, borders, flag), which clearly separates it from siblings like geocode, wiki, or fx_rates. An agent can identify this as the country-facts tool without opening the schema.

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?

Usage context is implied by the field list and data provenance ('world-countries dataset plus latest World Bank figures'), but the description never says when to prefer this over geocode, wiki, or fx_rates, nor does it state any exclusions or prerequisites. Adequate but leaves routing to inference.

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