search_keywords_by_source

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

Annotations provide readOnlyHint, idempotentHint, etc. Description adds: no aggregation, pagination ignored, invalid sourceKey returns HTTP 400, and a link to API spec. This adds meaningful behavioral context beyond annotations.

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 concise, front-loading the core purpose and return format. It includes a link but doesn't waste words. Slightly verbose due to the link, but overall efficient.

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?

No output schema, but description explicitly states return format {details:[{searchKeyword, percentage}]}, notes no time series, and flat share. With 3 params (1 required) and high schema coverage, this is complete. URL to spec adds extra completeness.

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%, so baseline is 3. The description adds context about sourceKey enum values (marketplace vs embedded-marketplace) and error case, and reinforces startDate/endDate usage. This extra value justifies a 4.

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 clearly states it returns top search keywords for one source, with specific details (flat keyword share, no time series). It naturally distinguishes from siblings like search_keywords_by_app by focusing on source-level.

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 explains when to use (for one source), mentions filters (startDate/endDate, no aggregation), and that pagination is ignored. It lacks explicit exclusions or direct alternative naming, but context is clear.

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