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

With no annotations, the description discloses the return structure (top-level keys as keywords, values as location-to-score maps), parameter defaults, and cost in tokens. It does not mention error handling or rate limits, but for a read-only fetch tool, this is sufficient behavioral insight.

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 organized with purpose first, then return format, then parameter constraints, and a cost note. Every sentence is informative, though the parameter section is slightly dense. No extraneous text, but it could be more streamlined.

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?

Given 8 parameters, no annotations, and an existing output schema, the description covers return format, defaults, and cost. It lacks explicit sibling differentiation and error handling, but for a moderately complex tool, it is reasonably complete.

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 the schema fully documents all parameters. The description paraphrases these details and adds the 'region requires a valid country' constraint, which is also present in the schema. It adds marginal value beyond the schema, so baseline 3 is appropriate.

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 the tool's function: 'Fetch Google Trends interest-by-region breakdowns for one to five keywords.' It specifies the resource (interest-by-region), the verb (Fetch), and scope (one to five keywords), effectively distinguishing it from sibling tools like interest_over_time and related_queries.

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 provides clear context on return format and parameter defaults, including the relationship between country and region. However, it does not explicitly contrast with sibling tools like interest_over_time or related_queries, so it lacks explicit when-to-use vs. alternative guidance.

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