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

Annotations already declare read-only, idempotent, open-world, non-destructive behavior, so the safety bar is covered. The description adds genuinely useful behavioral context beyond that: the 100-phrase batch ceiling and the cost model ($0.15 per successful call, failed calls free). Auth handling is left to the api_key schema field.

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?

Four tight sentences, front-loaded with what the tool returns, followed by capacity, use case, and price. No filler; each sentence carries decision-relevant information.

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, return values need no explanation, and annotations carry the safety profile. The description supplies the remaining decision inputs an agent needs: batch capacity, intended use, and cost, making it complete for a read-only data lookup.

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%, so all four parameters are already documented. The description only reinforces the batch limit ('up to 100 phrases'), matching maxItems, and adds nothing about language or location defaults beyond what the schema states. Baseline 3 is appropriate.

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?

States a specific verb and resource ('how many people search Google for each phrase per month') and enumerates the returned metrics (volume, cost per click, competition). No sibling tool overlaps this function, so the agent can identify it immediately.

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?

Gives a clear context for use ('pick keywords for a website, blog post, or ad campaign') but names no alternatives or exclusion conditions. Since no sibling covers keyword data, the absence of alternatives is low-risk, but explicit when-not guidance is still missing.

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