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

Annotations only cover the safety profile (read-only, idempotent, open-world); the description adds genuinely new behavior: summary/movers/droppedApps always span the full top 200 while `limit` truncates entries only, movement is empty on the first request for a chart, responses arrive within ~30s with a `stale: true` + `measuredAt` fallback, and no API key is needed but free-tier daily use is IP-limited. These are exactly the operational facts an agent cannot get from structured fields.

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 purpose and movement content are front-loaded, and each subsequent sentence carries a distinct operational fact (limit scope, first-day emptiness, 30s/stale behavior, auth tier). No sentence is filler or restates the name.

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 characterizes the response shape (summary, movers, droppedApps, per-app rank delta, measuredAt) and covers the freshness/staleness contract. Combined with a fully documented 5-param schema and safety annotations, an agent has everything needed to call it 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 description coverage is 100%, so the baseline is 3, but the description adds real semantics beyond the schema: `limit` truncates only the returned entries, not the summary/movers/droppedApps aggregates. It does not explain country/category key behavior beyond what the schema already states.

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 specific verb and resource with full scope: store-wide top charts (free/paid/grossing, overall or by category) plus day-over-day movement composition (rank delta, new entries, movers, drop-outs). That scope is unmistakably distinct from per-app siblings like sonar_app_rankings and sonar_keyword_rankings, so an agent can identify it without opening the schema.

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?

"Use to see what's rising in a market or category" gives a clear positive selection context. However, it names no alternative tool and states no when-not condition, so routing against near-neighbors (e.g. app-level rankings) is left to inference.

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