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

Annotations already signal read-only non-destructive behavior. The description adds beyond that by disclosing that results include accreditation status, ICANN enforcement actions, and the page and verbatim quote the information was read from, which tells the agent the tool returns source-backed evidence.

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?

Four sentences, each earning its place: a scoping prompt, the search mechanism with examples, the return payload, and the routing guidance. It is front-loaded and avoids filler.

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 only two parameters, a complete output schema, safety annotations, and explicit sibling routing, nothing essential is missing. The description fully equips an agent to select and invoke this tool correctly.

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% for both parameters, so the schema already documents them. The description adds value by clarifying query semantics: partial names, case-insensitive substring matching, and concrete examples like 'GoDaddy', 'Tucows', and 'namecheap'.

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: search ICANN's accredited-registrar register by name or IANA ID. It also gives concrete search examples and explicitly distinguishes itself from get_registrar, so an agent can tell them apart immediately.

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?

Directly provides routing guidance: 'Use this first when you have a name; use get_registrar when you already have the IANA ID.' This makes the selection decision explicit rather than leaving it to inference.

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