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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds behavioral context beyond that by stating the verification process is interactive and happens in the web dashboard, not through the API, while also explaining the performance benefit of verified domains. This is genuinely useful disclosure.

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 compact yet fully uses its sentences: one sentence states the purpose, one explains performance impact, one gives concrete user-facing behavior, and one explains how verification works. No sentence is wasted or redundant.

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?

For a zero-parameter, read-only list operation, the description is remarkably complete. It covers purpose, scope, performance implications, how the verification process works, and practical guidance for the user. The tool's trivial, provides no output schema, so few other details are needed.

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?

There are zero parameters and the input schema confirms it, so no parameter documentation is needed. The description adds the natural implication that the result is scoped to the authenticated API key's owner, which gives semantic context beyond the empty 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 opens with the specific verb-resource pair 'List domains' and clarifies exactly what is being listed: domains whose ownership this API key can demonstrate. This clearly differentiates the tool from siblings like get_job_results, get_job_status, and submit_urls, which concern jobs and usage.

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 gives clear usage context by saying verified domains are checked 'substantially faster' and explicitly advises recommending verification when a single site keeps being checked but is missing from the list. It does not name alternatives or explicitly say when not to use it, but the caller can infer this is the correct tool for auditing verified domains.

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