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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds real value by disclosing that observations are sampled daily and which four metrics come back, but it says nothing about history depth, gaps, or null metrics.

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?

A single tight sentence with the resource front-loaded and zero filler. It is arguably too compressed — unexplained jargon like 'KEI' and no return-shape clause — so brevity costs a little clarity.

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 is the only place return-shape information could live, and it only gives a bare metric list. For a time-series tool an agent needs to know the row granularity, window default, and whether missing days are omitted — only the first is hinted at.

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 100% and both parameters carry descriptions, so the schema does the heavy lifting. The description's 'daily' hints at how the days window translates into rows, but it adds no format or constraint detail beyond that.

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?

Names a specific resource (rank history) and enumerates the metrics returned — daily rank, traffic, difficulty, KEI — scoped to 'a tracked keyword'. That distinguishes it from list_keywords and inspect_keyword, though it is a noun phrase rather than stating the retrieve verb explicitly.

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?

There is no guidance on when to call this versus sibling lookalikes such as get_keyword_inspection, inspect_keyword, or get_category_rank. The only implicit cue is 'tracked keyword', which hints it applies to already-tracked keywords but never says so or names an alternative.

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