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

With no annotations, the description carries the full burden. It discloses that there are no request parameters, the return format (array with language_name and language_code), the mapping to upstream 'lang', and even the token cost. This is substantial transparency for a zero-parameter tool, though it could mention sorting or caching but that's minor.

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 four sentences, each with a specific purpose: stating the function, describing the return, noting the mapping, and giving the cost. It is front-loaded with the most important information and contains no filler.

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 zero-parameter list tool with an output schema, the description is complete. It explains what the tool returns, how it maps to the upstream API, its cost, and its intended use with sibling tools. 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 input schema has zero parameters, and the description explicitly confirms 'No request parameters,' aligning with the schema. Since there are no parameters to document, the baseline of 4 is appropriate, and the description adds value by explaining the output codes' purpose.

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 lists valid languages for use as the 'language' parameter in google-search.keyword_traffic_insights and google-search.url_traffic_insights, using a specific verb and resource. It distinguishes itself from sibling tools by naming the exact tools it serves, making its purpose unambiguous.

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?

It explicitly indicates when to use this tool: to retrieve language codes for the two named traffic insight tools. It provides clear context but does not mention alternatives or exclusion scenarios, which is acceptable for a simple lookup tool.

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