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

Annotations already declare readOnly/idempotent/non-destructive, so the safety bar is low, yet the description adds meaningful behavior: fixed 20-item pages for competitors ordered by visibility descending, pinned scan IDs across continuation, no limit argument, and restart-after-edit rules. It stops short of describing rate limits or partial-failure behavior, keeping it at a strong 4.

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?

The description is dense and front-loads an elliptical first sentence that is harder to parse than the operational sentences that follow. Most sentences carry useful constraints, but the structure is a flat run of terse statements with no clear hierarchy of what matters most.

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?

Because an output schema exists, return values need not be re-explained, and the description does cover several response-adjacent details (subjectContext, completedAt, percentage denominators). For a complex 15-parameter tool, though, it omits a plain statement of what the tool returns and any routing against alternatives, leaving it adequate but incomplete.

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 93%, so the schema already documents nearly all of the 15 parameters; the baseline is 3. The description adds only marginal filter semantics (e.g., denominators applied for brand, filters must stay unchanged across cursor pages) without compensating for anything the schema lacks.

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 ('Latest matching eligible Scan and change against the previous matching Scan') gestures at a comparative visibility overview but never states a clean verb+resource, and it reads as a description of mechanics rather than purpose. It does not distinguish itself from close siblings like get_visibility_timeline or get_scorecard, so an agent must infer which visibility tool to pick.

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?

There is real operational guidance – 'Follow nextCursor with unchanged filters' and 'Historical repairs and metadata edits require restarting' – which tells the agent how to keep pagination valid. However, it never says when to use this tool versus the other visibility/breakdown siblings, so selection guidance is only implied.

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