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

Annotations already declare open-world, non-destructive, and not read-only; the description adds the details that matter — the once-a-day refresh rate limit, the weekly cadence, that ranks past the first page (~11 apps) come back as null, and that the tool is free. That is real behavioral context beyond structured fields, though it doesn't explain what the refresh actually costs or what the response shape looks like.

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 scope and cadence come first and every sentence carries information, including the null-past-first-page rule. The only soft spot is the internal jargon 'open, gap, weak, and the ones it holds', which assumes knowledge of the keyword-status categories and could cost an agent a beat.

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 no output schema, the description does the necessary work: it explains what a record contains (rank per tracked keyword, per country), the time range, the null sentinel, and the refresh semantics. The main omission is `appId` guidance and any hint of the response grouping, which keeps it from a 5.

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 coverage is 67%: `country` and `refresh` already have schema descriptions, and the prose only reinforces them (default every storefront, daily cap on refresh). `appId` is undocumented in both the schema and the description, so the prose does not close that residual gap — a baseline 3.

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 names a specific resource (the app's App Store search rank), the dimension (per tracked keyword, per country), and the time scope (week by week, first read to latest). That is enough for an agent to tell it apart from keyword, visibility, and analytics siblings 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?

It establishes clear usage context: normal calls return the weekly series, while `refresh` performs a live country read capped at once a day. It does not name a competing sibling (e.g. visibility or search_positions) or state when not to use it, so it stops 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.