List countries

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

Annotations already declare read-only and open-world behavior. The description adds value by specifying the exact fields returned and the HTTP method, which gives the agent a clear expectation of the output format without needing an output schema.

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, information-dense sentence that includes the verb, resource, returned fields, and endpoint. No unnecessary words; it is perfectly concise for the tool's simplicity.

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 no parameters, no output schema, and rich annotations, the description is complete. It tells the agent exactly what to expect: a list of all countries with id, name, and code. There is no missing context for correct tool invocation.

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 has no parameters, and the schema coverage is 100% (empty schema). The description does not need to add parameter information. Per guidelines, 0 parameters yields a baseline of 4, and the description fulfills this.

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 tool returns all countries with specific fields (id, name, code) and even provides the endpoint, making the purpose instantly clear. It distinguishes itself from siblings like get_city or list_cities by focusing on countries only.

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?

While no explicit alternatives or when-not-to-use instructions are given, the description is sufficient because there are no sibling tools that list countries, so the usage context is unambiguous. It could benefit from stating that this is the primary tool for country data, but it's not necessary.

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