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

Annotations cover read-only, idempotent, open-world, non-destructive safety, and the description adds crucial behavior: cost model (one SERP fetch plus up to 10 live third-party fetches), result-bound limitation, error state semantics, and the fact that `scopeNote` is always returned. This goes well beyond what the annotations 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?

Front-loads the core operation, then cost, then state handling; every sentence carries operational information, including limitations and return shape. It is long but dense and free of filler, appropriate for the tool's complexity.

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 fully documents returned states, candidate statuses, platform classification, and scope limitations, so an agent can interpret results and handle errors correctly. Annotations already cover the safety profile, and 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 schema already documents all five parameters with descriptions. The description reiterates the brand/query and trackedDomain semantics but adds no syntax, defaults, or examples beyond what the schema provides, making the baseline 3 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: searches the free SERP backend for `brand` as a query, then checks each result page for a link to `trackedDomain`. This distinguishes it from siblings by defining exactly the unlinked-mention gap it measures.

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?

Explicitly instructs to check `state` first and warns that `serp_unavailable` must never be treated as zero mentions, which is a clear when-not caveat. It also frames the tool as free/no AI-gateway spend, but does not name alternative tools for the same job.

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