list_countries

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

Annotations already declare readOnlyHint=true, covering the safety profile. The description adds that results are scoped to a provider, which is a useful contextual detail, but it does not disclose additional behaviors like required permissions, error conditions, or output specifics. With annotations covering the key safety trait, a score of 3 is appropriate.

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, concise sentence that immediately states the tool's purpose. It is front-loaded with the action and resource, containing no filler or redundant information.

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?

An output schema exists, so return values do not need to be described. However, the description lacks details about the optional proxy_type parameter and how it affects the results, and it does not mention any prerequisites or context for the provider parameter. For a simple listing tool this is minimally viable but has clear gaps.

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 schema description coverage is 0%, meaning the description must compensate for parameter meaning. The description only mentions "with a provider" but does not explain the provider parameter or the optional proxy_type filter. This leaves both parameters semantically unexplained, providing no value beyond the bare schema.

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 uses a specific verb "list" and clearly identifies the resource as "countries/locations targetable with a provider." This distinguishes it from sibling tools like list_providers or get_provider_info, which focus on providers rather than country-level targeting.

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 description implies usage when you need to know which countries are available for a given provider, but it does not explicitly state when to use this tool versus alternatives, nor does it mention exclusions or conditions. This is an implied usage scenario, not explicit guidance.

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