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

With no annotations available, the description carries the full burden of behavioral disclosure. It meaningfully explains the return format as '[day, rank]' and clarifies the semantic difference between a null rank (absence from top results) and a bad rank, which is valuable non-obvious behavior. However, it does not mention rate limits, authentication, or the safe read-only nature of the operation.

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 two sentences with no filler. The core purpose is front-loaded, and the second sentence adds a precise, necessary interpretation of null values without extra verbosity.

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?

For a simple two-parameter tool with no output schema, the description covers the essential semantics: what the data represents secret, how the series is structured, and how nulls should be interpreted. Minor gaps such as date range, ordering, or default country behavior exist, but the tool is small enough that the description is largely sufficient for correct invocation.

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 both parameters are already documented in the schema. The description adds slight extra meaning by reinforcing the country scope ('for one country'), which helps clarify the optional-looking country parameter arena, but it adds no new detail about appId or formatting. This meets the baseline for schema-covered parameters without exceeding it.

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 phrase 'Keyword rank history for one country' clearly identifies the resource and scope, and it differentiates the tool from siblings like get_keywords, which likely lists keywords rather than time series. The description lacks an explicit verb like 'get', but the resource and purpose are unambiguous enough.

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?

The description implies that results are scoped to one country, which hints at the country parameter, but it provides no explicit guidance on when to prefer this tool over sibling tools such as get_keywords or get_charts. No alternatives or exclusions are mentioned, leaving the agent to infer the intended use case.

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