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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and non-destructive behavior. The description adds valuable behavioral context beyond those: it discloses that a plan-limit message is returned when rate limited or when the monthly quota is exhausted, and it describes the return values (0-100 plus volume). It does not cover authentication or any series-length/pagination behavior, leaving a minor gap.

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 description is four sentences with zero waste: purpose first, then usage alternatives, then rate-limit behavior. It is front-loaded and appropriately sized for the tool's complexity.

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?

Given the rich 100%-covered input schema and the absence of an output schema, the description is complete enough for correct invocation. It covers return format, rate-limit/quota behavior, and sibling alternatives, while the schema handles source-specific keyword formats and optional filters.

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 provides detailed parameter semantics for keyword, source, country, language, and resolution. The description only reinforces the one-keyword/one-source constraint and does not add syntax or conditional rules beyond what the schema already states.

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 verb and resource: 'Full historical series for one keyword and one source', and it clarifies the return shape (0-100 values, plus volume). It explicitly distinguishes itself from get_top_trends and get_growth, so an agent can identify its role without opening the 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 names the alternative for live 'what's trending now' boards (get_top_trends) and the alternative for most growth questions (get_growth), making the routing conditions explicit. This is exactly the when-to-use-this-vs-alternatives guidance needed.

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