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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds a note about the SimilarWeb v5 envelope (meta + data), which is useful for interpreting responses, but it does not disclose any other behavioral aspects like rate limits or authentication needs. The bar is lowered by annotations, so this is acceptable.

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 extremely brief, but the first sentence is a redundant tautology ('Referrals.') that adds no value. The second sentence about the envelope is useful but does not compensate for the missing purpose. It is not front-loaded with actionable information and feels under-specified rather than concise.

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 tool with 10 parameters and an output schema, the description is inadequate. It does not explain what referrals are, how the data can be used, or any specifics about pagination (though offset exists in the schema). The output schema covers return values, but the tool's purpose and typical use cases remain unclear.

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 all 10 parameters are individually documented. The description adds no additional parameter details, but the schema carries the burden effectively. Baseline of 3 is appropriate given high coverage.

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 'Referrals' simply restates the tool name and title without specifying what the tool retrieves or how it differs from the many other get_similarweb_* tools. The only substantive statement, about the response envelope, concerns format rather than purpose, leaving the agent to infer the tool's function.

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?

There is no guidance on when to use this tool versus any of the sibling SimilarWeb tools, no context about referral traffic, and no mention of limitations or prerequisites. The agent must guess which tool is appropriate for a given task.

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