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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, so the safety profile is covered externally. The description's only added behavioral content is cost transparency (estimated $0.6/request, $0.075 per credit, account-specific settlement), which is genuinely useful for an agent weighing calls. However, it discloses nothing about data scope, auth requirements, rate limits, or result characteristics of a demographics read.

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 text is short, but it is short because it contains no functional content at all — a pricing marker block rather than a front-loaded purpose statement. Conciseness here reflects under-specification, not efficiency; the pricing note should follow, not replace, a statement of what the tool does.

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?

An 8-parameter, 4-required data-retrieval tool with an output schema and a large sibling family needs at minimum a purpose statement and usage routing. The description supplies neither, leaving the agent unable to distinguish this from any other SimilarWeb endpoint. The only mitigating factor is that an output schema exists, so return shape need not be described.

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 only 13% across 8 parameters, with four required (domain, start_date, end_date, granularity) carrying no documented meaning in either schema or description. The description contributes zero parameter semantics — no date format, no granularity semantics, no explanation of main_domain_only or web_source — so it fails to compensate for the coverage gap.

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 contains no statement of what the tool does — it is entirely a pricing/billing boilerplate block. Nothing indicates that it returns SimilarWeb demographic data for a domain, and the title 'Demographics' is left to carry the whole purpose. An agent cannot determine the tool's function from the description text.

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, when not to, or how it relates to any of the ~30 siblings such as get_similarweb_audience_interest or get_similarweb_website_top_geographies. No prerequisites, no alternative routing, no exclusions.

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