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

Annotations already cover read-only/idempotent/non-destructive, and the description adds behavior beyond them: values are on a 0-100 scale with absolute volume when available, and a plan-limit message is returned on rate limit or quota exhaustion. It does not describe pagination or failure modes beyond the quota message, so not 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 purpose and the sibling routing in the first two sentences, then handles clarifications. Slightly padded by restating the preset-window format already enumerated in the schema, but nothing is wasted overall.

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?

No output schema exists, so the description correctly supplies return semantics (0-100 scale, optional absolute volume) and quota-limit behavior. Given six parameters with rich schema coverage, this is nearly sufficient; a bit more on what a per-source/per-window result collection looks like would close the gap.

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 carries the parameter burden with detailed per-source keyword formats, country/language/resolution restrictions, and the full preset list. The description only restates that windows are preset strings like '12M' and that sources can be multiple, adding no semantics beyond the schema — 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?

States a specific operation ('Point-to-point growth for a keyword on one or more sources') and immediately separates itself from get_time_series (full series) and get_top_trends (live app boards). An agent can distinguish this from every sibling without opening a 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?

Explicit routing: 'Designed for growth questions; for charting or custom math, get_time_series provides the full series.' It also preempts a likely confusion by clarifying that App Downloads/App Rankings are keyword sources here, not the live boards on get_top_trends.

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