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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), yet the description still adds real behavior: no interpolation or back-filling, only scans that actually ran are returned, oldest-first ordering, and an explicit billing statement ('FREE — charges no credits').

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?

Three sentences, front-loaded with what is returned before the comparison and the caveats. Each clause carries distinct information — payload, contrast with the sibling, empty/fill-in behavior, cost.

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 carries the return-shape burden and does it reasonably well: it names the fields seen per scan and the ordering, and explains empty results as scans accumulate. It stops short of stating volume limits or pagination, a minor gap for a history endpoint.

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 target matching semantics, the YYYY-MM-DD pattern for since, and the projectId provenance ('Get one from list_projects') are already documented. The description adds no parameter-level detail beyond that, which is the expected baseline when the schema does the work.

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 ('recorded AI-visibility history for one brand or domain') and enumerates the payload ('mentions, cited sources and competitors'), plus the ordering ('oldest first'). It is immediately distinguishable from run_brand_radar_scan and from the status sibling.

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 names the alternative and the condition that selects it: 'Answers whether visibility in AI answers is moving, which a single run_brand_radar_scan cannot.' It also sets a when-not expectation by noting the result is empty for a target never scanned.

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