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

Annotations already declare readOnly, idempotent, non-destructive, and openWorld, so the safety profile is covered. The description adds real interpretive context beyond that: confirmed chart exits are returned as nulls rather than omitted, revisions are immutable with primary-source provenance, and missing collection dates are gaps rather than zero values. This meaningfully changes how an agent reads results.

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?

A single dense sentence, front-loaded with the purpose, followed by qualifying clauses that each carry distinct information. The 'Pro:' prefix is slightly odd but does not waste much space.

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 seven parameters, no output schema, and no schema-level documentation, the description should do more to explain pagination (limit/offset) and the days window. It covers result interpretation well but leaves invocation semantics 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 0%, so the description carries the full burden. It references country/chart/depth identity and maps loosely to appId/store, but says nothing about days, limit, offset, or how country/chart filter the series. Four of seven parameters remain semantically unexplained.

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+resource: retained daily ranks and ratings, scoped to a single App Store ID or Google Play package. An agent can tell it retrieves historical rank/rating data for one app. It does not name or contrast with the sibling apps.attention, so it falls short of full sibling differentiation.

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?

No when-to-use guidance, no alternatives named, and no conditions that select this tool over apps.attention or market.history. The agent must infer usage entirely from the purpose sentence.

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