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

Annotations already declare readOnly, idempotent, non-destructive and open-world behavior, so the safety profile is covered. The description adds genuine behavioral context beyond that: snapshot comparison semantics ('change since an earlier snapshot'), the mover categories returned, and that movers.since may be null when no prior snapshot exists. It does not cover rate limits or cost, which keeps it from a 5.

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?

Front-loads the trigger condition, then parameters, then return shape, and sentences are information-dense with no filler. Slightly long as a single block, but every sentence carries content an agent can act on.

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 full schema coverage, rich annotations and an output schema, the essentials are already covered, and the description adds trigger guidance and snapshot semantics on top. Nothing needed to call it correctly is missing, though the return-shape recap partly duplicates the output schema.

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 schema already documents store/country/chart/genre/limit including formats, defaults and enum meanings. The description only lists the parameter names ('Pass store, country, chart, genre and limit') without adding syntax, defaults, or constraints beyond the schema, so the 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?

States a concrete verb and resource ('Read a top chart with movers') and grounds it in sample user utterances ('top free Productivity apps in the US', 'what is climbing the Health & Fitness chart?'). An agent can distinguish this chart-reading tool from siblings like app_tracker_lookup or app_tracker_keywords without opening any 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?

Opens with an explicit trigger condition ('Use this when the user asks what is on or climbing an App Store or Google Play top chart') plus two example phrasings, which is strong context. It stops short of naming when NOT to use it or pointing to a specific alternative sibling, so it falls short of a 5.

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