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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so safety is covered. The description adds value beyond that: result ordering ('ordered by estimated traffic'), the 100-keyword cap, and crucially a cost signal ('One lookup from the plan's allowance') that no annotation conveys.

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?

It is a single dense but front-loaded sentence with the core output described first and the competitor/cost caveats trailing. Every clause carries information, though the semicolon-chained structure is slightly heavy.

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 no output schema, the description does the work of explaining return values (keywords plus position, searches, visits, ranking page) and the competitors variant. It is nearly complete for calling the tool, missing only edge details like pagination or default behavior when competitor keywords are absent.

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 high (80%), so the baseline is 3, but the description still adds meaning: it clarifies that competitors=true returns domains sharing the most keywords, and that domain may be the user's site or a competitor. It reinforces the limit ceiling ('up to 100 keywords') beyond the schema's wording.

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 and resource ('What a domain ranks for in Google') and enumerates the returned fields (position, monthly searches, estimated visits, ranking page). This clearly separates it from keyword-centric siblings like keyword_volume and keyword_ideas, though it doesn't name those siblings outright.

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 gives a concrete when-to-use: 'Ask for a competitor's domain to find keywords the user's site is missing,' and explains the competitors=true variant. No explicit exclusions or named alternatives, so it stops short of a 5.

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