list_countries

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

The description implies a read-only operation with no side effects, but does not explicitly state that. However, since no annotations are provided and the tool is a data retrieval with an output schema, the description provides sufficient transparency about the returned data fields.

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 two sentences, front-loaded with the purpose, and each sentence adds necessary information. There is no redundancy or extraneous text.

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 simplicity (no parameters, output schema exists), the description is complete. It specifies what the list contains, leaving detailed return structure to the output schema.

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?

There are no parameters, and the description explicitly states 'no parameters needed', confirming the input schema. Schema description coverage is 100%, and the description adds the value of clarifying that no input is required.

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 a list of all countries with specific fields (ISO codes, calling codes, continent). It uses the verb 'Get' and resource 'list of all countries', distinguishing it from sibling list tools like list_currencies or list_languages.

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?

No explicit guidance on when to use this tool versus alternatives. The description is self-contained but does not mention limitations or when other tools might be more appropriate. For a simple, parameterless tool, this is minimally adequate.

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