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

Beyond the read-only/idempotent annotations, the description discloses a meaningful behavioral trait: values come from a shared cache and stale/missing terms cause a live upstream lookup that is billable. This directly informs cost-sensitive billing behavior and is exactly the kind of context annotations cannot provide.

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 concise and front-loaded with the core purpose, then follows with the important caching and billing caveat. Two sentences carry the full message with no fluff, though it could arguably be more structured with explicit parameter mapping.

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 input schema covers all parameters, an output schema exists, ans the annotations cover safety, the description adds the one missing strategically important piece: billing behavior around cache misses. Nothing essential for an agent to call this tool correctly 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?

Because schema description coverage is 100%, the schema already documents terms, country, and lang. The description adds practical semantics by stating the tool handles 'up to 50 search terms in one country' and stresses batching to avoid per-keyword bills, which gives extra meaning to the terms parameter beyond its schema constraints.

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 specifies the action ('Look up monthly search volume, keyword difficulty, CPC and competition level') and the resource (up to 50 search terms in one country). It differentiates the tool's overview function from keyword history or ranking tools, though it does not explicitly name sibling tools.

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 gives clear usage context: terms should be batched, max 50, single country at a time, and callers should avoid calling once per keyword. It does not explicitly say when to use this tool over sibling tools like get_keyword_history or list_keywords.

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