list_countries

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

With no annotations, the description carries the behavioral burden. It conveys a GET/list operation returning countries with counts, which signals a read-only action, but it does not describe ordering, pagination, or response behavior beyond what the output schema already covers.

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 a single efficient sentence and includes the useful endpoint. It is concise, though written as a noun phrase rather than a clear imperative sentence.

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?

The output schema covers return structure and all parameters are optional with defaults, so the tool is usable as-is. However, the lack of sibling differentiation and parameter semantics leaves an agent without enough context to confidently decide between this and list_country_codes or to customize ordering.

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 description coverage is 0% and the description does not mention order, reverse, or timeout. It neither defines valid values (e.g., what order options are accepted) nor otherwise compensates for the undocumented parameters.

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 identifies the resource ('countries in the directory') and a distinguishing feature ('with station counts'), plus the exact endpoint. It stops short of an explicit verb like 'lists' and does not contrast with list_country_codes, so it is clear but not fully differentiated.

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?

There is no guidance on when to choose this tool over closely related siblings such as list_country_codes or find_stations_by_country. The only usage signal is the implicit phrase 'with station counts', which is not enough.

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