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

Annotations already flag read-only, idempotent, and non-destructive; the description adds valuable behavior beyond these: data comes from a shared cache and that missing/stale terms trigger a billable live upstream call. This is a non-obvious side effect agents need to know before calling.

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 with no filler. The first sentence states the core function and constraints; the second delivers critical batching/billing guidance. Everything earns its place and is front-loaded.

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?

With an output schema present and annotations covering safety profile, the description fully covers when and how to invoke the tool. The billing/cache side effect and batch guidance are the only extra context needed, and both are present. Nothing an agent needs to call 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?

Schema description coverage is 100%; all three parameters have descriptions. The description reinforces limits (50 terms, one country) and adds behavioral guidance for the terms parameter (batch terms to avoid live lookup charges), which is meaningful value beyond the schema.

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 specific verb ('Look up') and a specific resource (keyword search-volume overview, including monthly search volume, keyword difficulty, CPC, and competition level), with explicit limits (up to 50 terms, one country). This clearly differentiates it from sibling tools like get_keyword_history or list_keywords.

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?

Offers clear usage context: batch terms rather than calling once per keyword, because missing/stale cache entries trigger a live, billable upstream lookup. It does not explicitly name alternative sibling tools for related lookups, so it falls short of a 5, but the cost and batching guidance is concrete and useful.

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