list_countries

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

With no annotations, the description carries the burden of behavioral disclosure. It accurately describes the action ('List all Nordic countries') but does not mention output format, ordering, pagination, or any potential side effects. For a simple read-only list, this is minimal but lacks depth.

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 short sentences with no filler. It front-loads the core purpose before adding a usage hint, making it concise and well-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 low complexity (no params, no output schema), the description provides enough to understand the tool's basic function and its intended role in the workflow (getting country IDs for filtering). It could specify the response structure, but overall it is reasonably complete for a simple list tool.

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 zero parameters, and the schema shows 100% coverage. The description's mention of 'country IDs' refers to output data, not input parameters, so it doesn't add parameter semantics. The baseline for 0 params is 4, and nothing reduces it.

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 that it lists all Nordic countries, which is a specific action on a specific resource. It distinguishes itself from sibling list_* tools by being focused on countries rather than instruments, markets, sectors, etc.

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 second sentence 'Use country IDs to filter instruments' provides a clear context for when to use this tool — to obtain IDs for filtering instruments elsewhere. However, it does not explicitly mention alternatives or when not to use it, so it is not a full usage guide.

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