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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), and the description adds substantial behavior on top: a hard 20 km examination cap, truncation disclosure via examinedMeters/truncated, and a note that ~25 calls for a 500 km trip fits the anonymous rate limit. That is real operational context an agent cannot get from the annotations.

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 front-loaded with the core behavior and the critical caveats, and every section is actionable. The 20 km limit is restated three times (cap, segmentation recipe, 500 km / 25 calls example), which is mild redundancy in an otherwise tight description.

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?

There is no output schema, so the description carries the burden of explaining returns — and it does, naming examinedMeters and truncated and telling the agent to report which portion was checked. Combined with the rate-limit note and geometry requirement, an agent has everything needed to call this correctly and interpret the result.

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, but the description adds meaning beyond the schema by tying the 20 km cap to lookahead_meters and by warning that a two-point polyline produces a straight-line check that will not follow the road. The corridor_meters and response_format parameters are left entirely to the schema.

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 opening sentence gives a concrete verb and resource: report suspicious-activity and stale-coverage locations along a supplied route geometry. That route-scoped framing implicitly separates it from point-based siblings like skimguard_find_nearby_activity and skimguard_regional_risk, but no sibling is named explicitly, so the differentiation is inferred rather than stated.

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 states the operating condition (route geometry required, 20 km examined), gives the correct workflow for longer trips (split into consecutive 20 km segments, one call each, then combine), and explicitly forbids calling a route clear unless fully covered. The straight-line-vs-real-geometry caveat is exactly the kind of guidance that prevents a wrong invocation.

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