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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint. The description adds behavioral context beyond these: it checks email authentication (SPF/DKIM/DMARC), looks for weak/missing auth, and mentions cache bypass via force_refresh. No contradiction with 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?

Two sentences with zero wasted words. First sentence states purpose with examples. Second sentence gives usage guidance and sibling distinction. Information is front-loaded and every sentence earns its place.

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 presence of an output schema (not shown but indicated), the description need not explain return values. It covers the tool's focus (email auth on TLD variants), differentiates from a key sibling, and addresses caching. No major gaps for a single-domain check tool with good annotations.

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%, so the schema already documents all three parameters. The description does not add per-parameter details, but it provides overall context that helps interpret the domain parameter. Baseline 3 is appropriate as the description adds no new param semantics.

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 clearly states the tool finds 'alternate TLD variants of a domain' with weak email auth for spoofing, using specific verbs and resource. It gives concrete examples (example.net, example.co) and explicitly distinguishes itself from the sibling tool check_lookalikes, making its purpose unambiguous.

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 explicitly says when to use it: 'when asked about TLD variants with email auth gaps'. It contrasts with check_lookalikes, providing clear differentiation. It does not mention prerequisites or when not to use, but the positive guidance is strong enough for a 4.

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