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

Annotations already mark it read-only and non-destructive, and the description adds substantial behavior: result ordering, what engine_shortfall means, that one_per_day filters to completed runs only, and a real limitation (at most 500 newest runs scanned, so results can fall short of `limit`). That truncation caveat is exactly the kind of non-obvious trait an agent needs.

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-loaded with purpose and ordering, then modes, then the caveat — a sensible progression. The single dense paragraph is slightly long and the engine_shortfall aside could be tighter, but every sentence carries information.

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 still conveys the return shape (a list of runs, each with the engines it queried and a `day` when one_per_day is used) and the engine_shortfall field's meaning. Combined with annotations, an agent has enough to call it and interpret results correctly.

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 goes further by explaining the semantics of one_per_day (completed runs, that day's latest, the run the Visibility page shows, inclusion of `day`) and how it interacts with `limit`. It says less about `time_zone` and `limit` bounds than the schema already does.

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 ('List visibility analysis runs for a domain') plus ordering ('newest first'). It also names two siblings (get-visibility-score, compare-visibility-runs) and how their ids relate, so an agent can separate it from those tools without reading schemas.

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?

Explains the two modes: a plain newest-first list versus one_per_day for completed-run-per-day retrieval matching the Visibility page, and points to the downstream tools that consume those ids. It gives clear context but never states an explicit exclusion or 'do not use this when' condition.

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