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

Goes well beyond the annotations: discloses the pricing model ($0.03 per company returned, charged only for what is returned, failed calls free), the default/cap on results (25/50), and how api_key behaves (leave empty for free tools or to get a payment link). Annotations already cover read-only/idempotent/open-world safety, so this is pure added value.

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?

Front-loaded with the core purpose and a concrete example, then layered with limits, filters, use case and pricing. Slightly redundant in stating the pay-per-returned-site rule twice ('you pay only for sites returned' and again in the Price sentence), which costs a point on tightness.

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?

Covers everything an agent needs for a discovery tool with an output schema present: what it returns (phone, emails, social profiles), how many, cost, and filter surface. Since an output schema exists, return-value detail need not be spelled out further.

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 the schema already documents limit, country, keyword, technologies and api_key with examples and constraints. The description restates the default 25 / up to 50 limit and mentions country/keyword filtering but adds no new syntax or conjunction semantics beyond what the schema says. Baseline 3 applies.

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 ('Build a lead list of websites that use specific software') and immediately grounds it with concrete examples ('every Shopify store using Klaviyo, or dental sites on WordPress'). This distinguishes it from the neighboring per-site tech_stack tool, which inspects one known site rather than discovering sites by technology.

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 clear intended context ('Use it to find prospects who already use (or need) what you sell') and notes the country/keyword filters, so the agent knows when this is the right tool. It stops short of naming alternatives or stating when NOT to use it (e.g. use tech_stack to inspect a known domain), so not a 5.

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