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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, but the description adds substantial behavioral context beyond that: fully passive DNS and CT-log checks, no traffic sent to target or lookalike domains, no API key required, rate limiting, and a crucial interpretive framing that a registered lookalike is exposure to verify, not an accusation. This is rich, useful, and consistent with 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 longer than average but every section earns its place: the passive-safety note, the non-accusation framing, the output summary, and the sibling routing are all decision-relevant. It is front-loaded with the core purpose and only slightly dense in the middle.

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?

Given the single parameter, rich annotations, and an existing output schema, the description covers everything an agent needs: method, scope, safety, framing, rate limits, auth requirements, output composition, and alternative tools. Nothing critical is missing for correct invocation.

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%, and the domain parameter is already well documented in the schema, including the registrable-domain expectation and scheme/path stripping. The tool description reinforces the input but does not add 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 opens with a specific verb and resource: 'Assess how exposed a domain is to brand impersonation and phishing.' It further distinguishes itself by naming sibling tools: 'Use lookalike_domains or subdomain_discovery for the raw per-tool detail,' making clear this tool returns an aggregate grade rather than raw findings.

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?

The description clearly states when to use this tool versus alternatives by pointing to lookalike_domains and subdomain_discovery for raw detail. It also implies an overall assessment use case with the A+ to F grade. It stops short of explicit when-not-to-use conditions or other sibling exclusions, but the guidance is strong.

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