REST Countries — Countries by Region

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

Annotations already declare the tool as readOnlyHint, idempotentHint, openWorldHint, and non-destructive. The description adds context about the data returned (population, area, capital, currencies) and mentions subregions, but does not detail behavior like pagination or output limits. It does not contradict annotations.

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 concise: two sentences and a list of arguments. It front-loads the purpose and key details. However, the second sentence is a bit cluttered with 'Args:' and enums, and could be more structured.

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?

Given the tool's complexity (4 parameters, no output schema) and rich annotations, the description provides a coherent overview: it states what the tool does, what fields are returned, and lists main arguments. It is missing explicit detail on limit and response_format behavior, but overall it is informative enough for an agent to use the tool correctly.

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?

With 0% schema description coverage, the description must compensate, but it only lists parameter names and enums without explaining semantics. For example, 'limit' and 'response_format' are not described beyond their possible values. The agent gains little additional meaning beyond the schema's defaults and enum constraints.

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 clearly states the action ('List all countries') and the resource ('in a region'), and provides specific details like the fields returned (population, area, capital, currencies) and example regions. It distinguishes itself from sibling tools like globalpulse_countries_get_profile, which focuses on a single country.

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 lists valid regions and subregions, and enumerates arguments, but does not explicitly compare this tool to siblings or state when to use it versus alternatives. The context implies it's for listing countries by region, but lacks explicit when-not-to-use guidance.

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