Look up the companies behind many domains

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

The annotations only indicate read-only and open-world hints. The description adds valuable behavioral detail: results come as a compact table, duplicates and www variants collapse and are charged once, and misses/malformed domains are free. Pricing behavior is disclosed clearly and does not contradict the annotations.

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 compact and front-loaded with the core purpose followed by usage guidance and cost details. Every sentence earns its place, and the key differentiator (one call for up to 20 domains) appears immediately.

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 single-parameter read-only tool with no output schema, the description covers purpose, scope, batching behavior, deduplication, pricing, and free cases. Nothing essential for an agent to decide whether and how to call it is missing.

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%, and the schema already documents that domains are an array of strings, bare domains, with maxItems 20. The description reinforces this but adds no new parameter-level meaning beyond what the schema provides, so the baseline of 3 is appropriate.

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 states a specific verb ('Look up'), a clear resource (companies behind domains), and a distinguishing scope (up to 20 domains in one call). It also differentiates from the singular sibling by emphasizing the batch capability, so an agent can immediately tell it apart.

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 explicitly says to prefer this over repeated lookup_company calls when several domains are already known, and explains the efficiency and cost equivalence. This provides direct routing guidance versus the main alternative.

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