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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds real value beyond them: it discloses the shape of the returned verdicts (reason, currency relative to the app's present listing and the category's present definition) and warns that missing_since means the app is off the App Store. It stops short of saying anything about response size, cost, or what happens for an unranked app.

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?

Two sentences, no filler: the first front-loads the payoff (the ranking breakdown), the second delivers the safety caveat. The first sentence is a dense nested list that takes a moment to parse, but nothing in it is redundant.

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 only two fully-documented parameters and no output schema, the description carries the burden of describing return content and does so in detail (score components, ranks, verdicts, history). The missing piece is guidance on which key form to prefer or what comes back when the app has no ranking at all.

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 'key' (app slug or numeric app_store_id) and 'list' (optional category slug) are already fully documented. The description's 'per category' hints at the list filter but adds no format, defaulting, or validation detail beyond the schema, so baseline 3 applies.

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 purpose (explaining why an app ranks where it does) and enumerates exactly what the explanation contains: score components per category, per-store ranks, judge verdicts, and change history. That content list implicitly separates it from siblings like get_app or recent_changes, but it never names an alternative explicitly.

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?

Usage is only implied by the framing 'Why an app sits where it does' — an agent must infer that this is the tool to reach for when a ranking needs justification rather than raw app data. The one explicit directive is about downstream behavior ('do not recommend it or send anyone to its store_url' for delisted apps), not about when to pick this tool over a sibling.

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