List countries

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description goes beyond that by disclosing the sort order (station count, highest first) and the fact that only countries with currently working stations are included, which is real behavioral context.

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?

A single well-formed sentence that front-loads the scope (countries with stations) and closes with the ordering rule. 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?

With an output schema present, the description need not explain return values, yet it usefully summarizes them anyhow. Scope, ordering, and the working-station filter are all covered; only when-to-use guidance against sibling tools is absent, which is a minor gap for a simple read-only listing.

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 100%, so limit and min_stations are fully documented in the schema itself. The description adds no syntax or format detail for either parameter, so the baseline 3 applies; the mention of station counts loosely relates to min_stations but adds no new semantics.

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?

Specific verb (List) plus resource (countries) with explicit scope: only countries that have internet radio stations in the directory. It also enumerates the payload (ISO 3166-1 alpha-2 codes, working-station counts, 72FM page), which distinguishes it from siblings like search_stations and list_genres that operate on different resources.

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 purpose implies a discovery/browse role, so an agent can infer this is the entry point for enumerating countries before filtering stations. However, it never states when to prefer this over siblings such as list_genres or search_stations, nor any prerequisite or exclusion. Usage is only implied.

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