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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds value by stating the free credit cost (0 credits) and explicitly naming the argument it relates to, which is useful behavioral context beyond 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?

The description is a single, efficiently worded sentence that front-loads the core information (what codes are returned) and includes examples and cost. No wasted words or 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?

For a simple zero-parameter tool, the description is sufficient: it explains the output content and gives examples. It does not specify the exact return format (e.g., array of strings), but given the simplicity and absence of an output schema, this is a minor gap. The mention of the argument name and credit cost adds enough context for an agent to use it correctly.

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 baseline is 4 per the rules. The description does not need to add parameter details since there are none; it correctly focuses on the output.

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 states a clear purpose: it returns all country/language codes accepted by the `country` argument, with concrete examples. This is distinct from any sibling tool, which all deal with SEO/analytics operations rather than enumerating valid parameter values.

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 implies when to use this tool: when you need to know which codes are valid for the `country` argument. It also notes the tool is free (0 credits), which is a relevant usage consideration. However, it does not explicitly mention when not to use it or name alternatives, though no direct sibling exists for this functionality.

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