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

Annotations already establish the safe, read-only, idempotent profile, so the bar is lower. The description then adds genuinely useful interpretive behavior: series with different comparison keys are not comparable, and gaps mean missing runs rather than zeros. That prevents an agent from misreading the data, though nothing is said about auth scope or result size.

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?

Two tight sentences with the purpose front-loaded and no filler. The second sentence is dense but every clause carries operational value; only the omission of sibling routing keeps it from being exemplary.

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 9 parameters at 0% schema coverage, no output schema, and no sibling differentiation, the description is underspecified for a tool of this complexity. It omits the meaning of the cohort enum and the granularity/engine dimensions that define what the returned points actually are.

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 0% across 9 parameters, so the description must carry the load and largely does not. "Explicit window" loosely maps to from_at/to_at and "comparison keys" gestures at cohort/engine/market_id, but granularity, transport_model, retrieval_enabled, and the core-vs-comparison cohort meaning are entirely unaddressed.

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 resource and dimension: visibility measured over time (a trend/time-series read). This is clearly distinct from a snapshot-style read, but it never names or contrasts the adjacent siblings read_visibility_overview, read_visibility_results, or read_visibility_sources, so an agent must infer when this one applies.

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?

"For an explicit window" implies that from_at/to_at must be supplied deliberately rather than defaulted, which is a usable hint. However there is no when-to-use/when-not guidance and no routing to alternative visibility tools, so usage is only implied.

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