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

Annotations already declare readOnly, idempotent, and closed-world, so the safety profile is covered. The description adds meaningful scope beyond that: the result is scoped to the signed-in brand and includes trend/movement data, which tells the agent what kind of read this is.

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?

Two sentences with no redundancy: the first states the payload, the second states the trigger conditions. Content is front-loaded with the returned data rather than preamble.

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?

With no input parameters and no output schema, the description is the only source describing what comes back, and it does so at a useful level (index, per-engine presence, movement). A little more on freshness/period or comparison basis would fully close the gap, but it is largely 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?

The tool takes zero parameters, so there is no parameter semantics burden to carry; the baseline of 4 applies. Nothing in the description misleads about inputs.

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?

Names a specific resource (the signed-in brand's visibility index) and enumerates what the response contains: per-engine presence and movement over time. This is clearly distinguishable from siblings like my_brand or my_questions, which cover brand identity and question lists respectively.

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?

Gives explicit triggering conditions: 'when the user asks how they are doing, whether anything changed, or how they compare to their category.' That is solid when-to-use guidance, though it never names an alternative sibling tool for the comparison case, which other tools in this server may cover.

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