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

Annotations already provide readOnlyHint: true, and the description adds real behavioral detail: summary/movers/droppedApps always reflect the full top 200 even when limit truncates entries, movement is empty on first request, and it works without an API key with free-tier limitations. This goes well beyond what the schema or annotations alone reveal.

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 front-loaded with a precise, actionable sentence and follows with a short use-case and essential caveats. Every sentence carries distinct value and there is no filler, repetition, or unnecessary background.

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?

For a read-only tool with no output schema, the description compensates by naming the key result concepts (per-app rank delta, new apps, biggest movers, dropped apps) and explaining the important edge cases around first requests and the full top-200 aggregation. Together with the fully described input schema, this gives an agent enough context to select and invoke the tool 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?

The schema already documents all five parameters with 100% coverage, so the baseline is 3. The description adds important semantic context about how `limit` interacts with the summary/movers/droppedApps aggregates and the first-request behavior, which helps an agent understand parameter consequences without overstepping 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?

'Get a store top chart' names a specific verb, resource, and scope (free/paid/grossing, overall or by category) and adds movement details that distinguish it from a generic rankings tool. It is clearly purposeful, but it does not explicitly name alternative sibling tools or state why it should be preferred over them.

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?

The description explicitly says 'Use to see what's rising in a market or category,' which gives a concrete usage context. It also provides useful edge-case guidance (first-snapshot behavior, no API key needed), but it does not explain when not to use it or direct the agent to sibling alternatives.

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