check_shadow_domains

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint false, so the description doesn't need to repeat them. It adds that the tool flags weak/missing email auth for spoofing, which is useful context. 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, front-loaded with the primary action and immediately followed by usage guidance. Zero wasted words; 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?

With output schema present and good annotations, the description covers the core purpose and distinction from sibling tools. It doesn't explain return values (output schema handles that) or edge cases, but for a check tool this is sufficiently complete. Could mention limits like scope of TLDs, but not necessary.

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 the schema already describes all three parameters (domain, format, force_refresh). The description doesn't add parameter-specific meaning beyond what the schema provides, so the baseline of 3 applies.

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 states a specific verb ('Find'), resource ('alternate TLD variants of a domain'), and purpose (weak/missing email auth for spoofing), and explicitly distinguishes from 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?

It provides clear guidance: 'Use when asked about TLD variants with email auth gaps' and contrasts with check_lookalikes, which is a concrete alternative. This tells the agent exactly when to use and when to avoid.

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