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

The annotations (idempotentHint true, destructiveHint false, readOnlyHint false) already indicate a non-destructive, idempotent mutation. The description adds valuable context beyond annotations: 'Only provided fields change' clarifies partial update semantics, 'Not metered' provides cost/usage behavior, and 'requires a free Prowlo account — call it to get a signup link' discloses an authentication requirement. These additions go beyond what the annotations capture.

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 compact and front-loaded: the first sentence states the core purpose and scope, followed by three short, informative clauses. Every sentence earns its place, providing the partial-update behavior, metering note, and account requirement without any fluff.

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 description is reasonably complete for an update tool with no output schema. It covers the purpose, partial-update semantics, metering, and auth requirement. It does not describe return values or error handling, but those are not required by the output schema. Given the nested query object, one could argue for more detail, but the schema already documents the query shape in depth.

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?

The input schema has 100% description coverage, so each parameter already carries a description. The tool description adds minimal parameter-level information, focusing only on the list of fields (name, query, interval, window) and the partial-update behavior. With high schema coverage, a baseline of 3 is appropriate; the description does not add significant new 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 clearly states the action ('Update') and the resource ('Trend'), and also lists the specific mutable fields (name, query, interval, window). This makes it unambiguous and distinguishes it from sibling tools like trend_create or trend_delete.

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 usage by saying 'Update a Trend' and 'Only provided fields change', which suggests a partial-update pattern. However, it does not explicitly say when to use this tool versus alternatives like trend_create or trend_delete, nor does it mention any prerequisites or context beyond the account requirement.

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