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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds behavioral context beyond that: it specifies that only countries with public-holiday data are included, and it clarifies the data's intended downstream use with get_holidays. This adds value without contradicting the 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?

Two sentences, zero filler. The primary purpose is stated first, followed by a direct and actionable link to the sibling tool. Every word earns its place; no redundancy or unnecessary detail.

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?

For a no-parameter, read-only listing tool with an output schema (indicated by 'Has output schema: true'), the description fully covers what an agent needs: what the tool returns (country codes) and how to use the result (in get_holidays). Nothing essential is missing.

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, so the schema is trivially complete. The description has no need to elaborate on parameters and doesn't attempt to. The baseline of 4 for zero-parameter tools is appropriate, as there is nothing more to explain.

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 resource ('country codes that have public-holiday data'), making the purpose immediately clear. It also distinguishes itself from siblings by explicitly referencing get_holidays, which is the only other holiday-related tool, so an agent can easily tell them apart.

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 provides clear context for when to use this tool (to obtain country codes) and even instructs the agent to use the resulting code as the 'country' parameter in get_holidays. It doesn't explicitly state when NOT to use it, but the use case is so unambiguous that no exclusion is needed.

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