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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: the result set is capped ('up to 60 by rating count') and totals are computed by adding the ranges, which tells the agent about aggregation semantics and limits.

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?

Three tightly packed sentences: usage trigger first, then input options, then return shape. The example query earns its place by disambiguating the intent, and there is no filler.

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 aggregate tool with an output schema present, the description covers when to call it, the mutually exclusive inputs, the 60-item cap, and the aggregation behavior. Nothing an agent needs in order to invoke it correctly is missing.

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 3 baseline applies. The description goes slightly beyond by clarifying that 'app' can be any App Store app belonging to the developer (not necessarily a specific one) and that developer is an id, which makes the anyOf either/or contract clearer than the schema alone.

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 verb and resource ('estimate a developer's apps earn together') and explicitly positions itself against the sibling app_tracker_estimate by noting it returns 'the same revenue and download ranges as app_tracker_estimate, plus totals'. An agent can distinguish the publisher-level aggregate from the single-app estimator without opening either 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?

It gives an explicit trigger condition ('when the user asks what a developer's apps earn together'), a concrete example query, and routing guidance for the alternative inputs ('Pass app... or developer'). The reference to app_tracker_estimate implicitly names the single-app alternative, so selection is unambiguous.

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