get_supported_countries

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

No annotations provided, so the description carries full burden. It discloses critical behaviors: subdivision codes are case-sensitive and must be used verbatim, country codes are case-insensitive, and subdivisions may be empty for some countries or due to library errors—all beyond basic functionality.

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?

Description is well-structured: first sentence for purpose, then usage guidance, then important behavioral notes, then return format. Every sentence adds value without redundancy.

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?

Despite no parameters and no annotations, the description is thorough. It explains the return structure (countries list with code, name, subdivisions, total) and addresses edge cases (empty subdivisions, library errors), making it complete for agent interaction.

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?

Tool has zero parameters, so baseline is 4. Description does not need to add parameter info, but it does mention how subdivision codes (from other tools) are used, which is helpful context.

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?

Description clearly states 'List all countries supported by the holidays library, with subdivisions' with a specific verb and resource. It differentiates from sibling tools (which focus on business days, dates, holidays) by positioning itself as a discovery tool.

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?

Explicitly advises using this tool 'before calling any country-aware tool', and explains that it provides valid ISO codes and subdivision codes for other tools, effectively guiding when and why to use it.

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