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

Annotations already declare readOnlyHint=true, yet the description still adds real behavior: ascending chronological order, omission of days without a measurement, and a plan-based cap. No pagination or response-size caveats are mentioned, keeping it just short of full disclosure.

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 tightly packed sentence that leads with the returned data, then ordering, gap handling, and plan limits. No filler.

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 carries the return shape itself (three metric series per day) and does so completely; the only missing piece, a sample record layout, is beyond what a definition needs.

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%, and the description fills the notable hole by explaining the provenance of keywordId (from get_app_keywords), which the schema leaves undocumented. The days parameter and its free-plan cap are already in the schema, so the description correctly stays silent there.

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 verb and resource (daily rank/popularity/difficulty history for one tracked keyword) and distinguishes itself from get_app_keywords by naming the sibling as the source of keywordId. Ordering ('oldest first') and gap behavior are also specified.

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?

Tells the agent to obtain keywordId from get_app_keywords and warns that free plans are limited to the last 7 days. It gives clear context for use but does not explicitly exclude alternatives like get_keyword_popularity or get_most_searched_keywords.

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