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

Annotations already declare readOnly, idempotent and non-destructive, so safety is covered. The description adds genuinely non-obvious semantics: rank_change is a positive-gain delta, and it is null (not 0) both when there is no previous day and when the keyword entered or left the observed depth — this prevents a real misinterpretation of the returned data.

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, front-loaded with the returned field set, then a single dense but purposeful clarification of rank_change. No filler, though the parenthetical explanation of rank_change is compact enough to require a careful read.

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 compensates by naming the returned fields, and annotations cover the safety profile. However, it says nothing about pagination, ordering, default scope when no filters are supplied, or result size limits — real gaps for a zero-required-parameter list tool.

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% — store, country and application_id are all documented in the schema, including the GOOGLE_PLAY_SOURCE prerequisite. The description contributes nothing about parameters, 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?

The description clearly identifies the resource as tracked keywords and enumerates the returned fields (rank, traffic, difficulty, KEI, favorite flag, movement), which makes the operation unambiguous. It never names a sibling (e.g. get_competitor_keywords, list_keyword_opportunities, inspect_keyword) to differentiate scope, nor states the verb 'list' explicitly, so it stops short of a 5.

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 word 'tracked', which distinguishes this from discovery/search-oriented siblings, but there is no explicit when-to-use, when-not-to-use, or named alternative. An agent can infer the scope but must reason about it rather than being told.

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