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

No annotations were supplied, so the description carries the full burden and does so well: it declares read-only status, the per-TLD result values (registered/available/unknown), parallel checking, and even the underlying RDAP semantics (404 means not registered, 'unknown' means no RDAP service). It does not mention rate limits, latency, or failure modes for network errors, which keeps it from a 5.

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, then result shape, then mechanism, then scope caveat and sibling routing — a sensible order. It is dense but not padded; the only mild redundancy is repeating the default TLD list that the schema already provides.

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 no annotations and no output schema, the description compensates by explaining the return format (one JSON result per TLD with three possible values) and the domain-vs-trademark boundary. An agent has everything needed to call it correctly and interpret the response.

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 both parameters are already documented with examples and the default TLD list, so the description adds little beyond restating the default set and the custom-list option. Baseline 3 is appropriate where the schema does the heavy lifting.

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 ('Check whether a brand name is free to register as a domain') and immediately differentiates itself from the sibling screen_trademark by scoping itself to domains, not trademarks.

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?

Explicitly names the alternative tool and the condition that selects it: 'use screen_trademark for the trademark check'. It also warns what this tool does not establish (a free domain does not mean the trademark is clear), which prevents the most likely misuse.

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