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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety and open-world profile is covered without description help. The description adds the useful hint that the query is 'typically a domain', but discloses nothing further about return behavior, data scope, or coverage, which is acceptable given the output schema exists.

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 short sentences, zero filler, with the core purpose front-loaded and the routing hint second. Every sentence earns its place.

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 an output schema covering return values and annotations covering safety, the description only needs to convey purpose, query shape, and sibling routing — all of which it does. It falls just short of full completeness because 'data' remains under-specified and the when-to-use-vs-alternative condition is not stated.

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 baseline is 3, and the description earns above baseline by clarifying the otherwise vague schema text 'Similarweb search term' as typically a domain. That is meaningful added semantics for the single parameter.

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?

States a specific verb and resource ('Returns SimilarWeb data for a given query') and explicitly distinguishes itself from the sibling similarweb_web. The only weakness is that 'data' is generic, so an agent knows the source but not precisely what shape of data it gets without checking the output schema.

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?

It names the alternative (similarweb_web for Web Info), which implies this tool is the non-web-info variant, but it never states the condition under which an agent should pick this tool over that one. Usage is implied rather than explicit.

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