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

With readOnlyHint and openWorldHint already covering the safety profile, the description adds useful context: the result is an SAP score from 0 to 100, data spans both stores, and the call costs 4 credits. It does not elaborate on latency or the exact return shape, but the schema covers the cache/live behavior.

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 definition is front-loaded with the core purpose, then immediately gives the alternative and cost. Every clause adds useful selection or behavioral information with no waste.

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 one-keyword metrics lookup, the description covers purpose, scope, return range, cost, and the key alternative, while the schema fully documents the three parameters and annotations cover safety. Any remaining ambiguity about whether 'across both stores' yields a single score is minor.

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 country, keyword, and cache are already well documented. The description reinforces that the lookup is for one keyword in one country, but adds no new syntax or format meaning beyond the schema.

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 states a specific verb (Get) and a precisely scoped resource: search-ads popularity (SAP, 0-100) for one keyword in one country across both stores. It explicitly distinguishes itself from the sibling keyword_metrics by noting that keyword_metrics adds difficulty and languages.

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?

It clearly frames this as the cheapest popularity-only check and names keyword_metrics as the alternative when difficulty and languages are also needed. That gives an agent an explicit selection rule rather than leaving usage to inference.

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