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

Annotations already declare readOnlyHint and openWorldHint. The description adds credit cost and a higher deep cost, which is useful behavioral context, but it does not explain auth requirements, rate limits, or what deep changes beyond the schema.

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?

One terse sentence with no filler; the output list and cost are front-loaded. However, the fragment style and ambiguous 'deep 30' reduce clarity slightly.

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 output schema exists, so return values need not be explained. Still, for a lookup tool with a sibling related_domains and an undocumented domain parameter, the description omits usage and parameter details, leaving gaps.

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 50%: deep is documented in the schema, while domain is not. The description only adds 'deep 30' cost, not domain format or deep semantics, so it does not compensate for the undocumented domain parameter.

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 enumerates specific outputs (domain age, lookalike-brand technique, abused TLD, blocklist status, verdict), making the resource and value clear. However, it is a noun phrase without an explicit verb and does not distinguish this from related_domains or other lookup_* siblings.

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?

No guidance is given on when to use this tool versus related_domains or other lookup tools; only cost is mentioned. The agent must infer usage from the name and title.

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