Citable — the keywords a domain ranks for

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

With readOnlyHint and openWorldHint annotations already covering safety, the description adds valuable behavioral context: the per-call cost, the fact that it is not charged on failure, the exact output content, and ordering. This goes beyond what annotations or schema 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 compact and front-loaded: cost comes first, then the core function and output details, then the competitor use case, then the no-charge behavior. Every sentence earns its place and there is 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?

Even without an output schema, the description enumerates the returned data (volume, CPC, position, movement, URL, total count), sort order, pricing, and intended use. For a read-only lookup tool with fully documented parameters, 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?

Schema coverage is 100%, so the baseline is 3. The schema already documents domain, lang, limit, and country with defaults and limits; the description does not add parameter-specific meaning beyond what the schema contains.

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-resource combination: the keywords a domain actually ranks for, with explicit fields (volume, CPC, position, movement, ranking URL) and sort order (highest volume first). It differentiates from sibling tools like keyword_suggest or keyword_research by emphasizing 'actually ranks for' rather than suggestions or metrics.

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 a clear use case: 'Point it at a competitor for their playbook,' and the phrasing 'actually ranks for' implies this is for observed rankings rather than keyword ideas. It does not explicitly name alternatives or state when not to use it, but the context is clear enough for an agent to route correctly.

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