check_shadow_domains

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

Annotations already indicate readOnlyHint and idempotentHint. The description adds behavioral context about checking email authentication, but does not detail caching, rate limits, or output specifics. Since output schema exists, it's adequately transparent.

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 two sentences: first defines the action and scope, second provides usage guidance and differentiates from a sibling. No wasted words, very efficient.

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 and high schema coverage, the description covers key aspects for tool selection and invocation. It could be slightly more specific about what constitutes 'alternate TLD variants', but overall sufficient.

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% with all parameters described. The description does not repeat parameter details beyond what the schema provides, meeting the baseline expectation. No additional value beyond schema.

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's purpose: finding alternate TLD variants of a domain that have weak email authentication for spoofing. It uses a specific verb ('Find'), specifies the resource (domain), and distinguishes itself from the sibling check_lookalikes.

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 'Use when asked about TLD variants with email auth gaps' and contrasts with check_lookalikes, providing clear context for when to employ this tool.

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