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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description usefully adds behavioral content beyond that: the returned values are ISO alpha-3 codes and the list deliberately includes World Bank aggregates such as WLD and EUU, which an agent would not guess.

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, zero waste. The core statement comes first and the clarifying detail about region codes follows, so an agent gets the essential fact immediately.

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 zero-parameter listing tool whose annotations already cover the safety profile, the description is nearly complete. With no output schema, it does describe the shape of returned values, though it could state whether the full list is always returned or whether results are paginated/limited.

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 tool takes zero parameters, so there is nothing for the description to disambiguate — baseline 4 applies by rule.

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 verb and resource ('Lists the countries and regional aggregates in EconDash') and specifies the identifier format returned (ISO 3166-1 alpha-3 with names). It is clearly distinguishable from siblings like compare_countries and get_indicator_series, though it never explicitly names an alternative.

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 is only implied: this reads as a code-lookup/discovery tool, useful before calling compare_countries or get_indicator_series, but the description never says when to use it or when not to. No prerequisites or exclusions are given.

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