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

Given the readOnlyHint and idempotentHint annotations, the description still adds useful behavioral detail by describing the exact result string, including the boundary behavior: 'not in top N' if the app is absent from the scanned results. This clarifies how the optional num parameter affects the outcome.

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 a single, tightly worded sentence that front-loads the purpose, then provides the expected return format and edge-case behavior. Every clause adds value and there is 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?

The tool has strong annotations, an output schema, and a sufficiently descriptive parameter schema, so the description does not need to explain every return field. It covers the main lookup goal and the most important edge case (app not found), making it adequate 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?

Although schema coverage is 100%, the description adds important meaning by clarifying that 'term' is the keyword, especially since the schema text for 'term' appears mislabeled as a language code. It also connects 'num' to the 'top N' behavior, which helps the agent understand the parameter's practical effect.

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 uses a specific verb ('Look up') and identifies the exact resource: the current ranking of a specific Appskyline app for a keyword in a given store and country. It clearly distinguishes this from sibling tools such as get_keyword_history or get_keyword_overview by emphasizing 'current ranking.'

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 context is clear: this is the tool to use when you need a current, point-in-time rank for a specific app-keyword-store combination. It does not explicitly name alternatives or when not to use it, but the 'current ranking' phrasing makes the intended usage obvious enough.

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